Profitable Farming
of Beef Cows
Editors: Steve Morris
and Duncan Smeaton
2009
Profitable Farming of Beef Cows
Steve Morris and Duncan Smeaton
Profitable Farming of Beef Cows
Written by:
Steve T. Morris, Massey University, Palmerston North, New Zealand and
Duncan C. Smeaton, AgResearch, Ruakura Research Centre, Hamilton, New Zealand
Special thanks are expressed to the following writers who also contributed:
•
John Meban, Veterinarian, Gisborne
part Chapter 4
•
Chris Morris, AgResearch, Ruakura
part Chapters 2 and 4;
sundry technical advice and accuracy checks
•
David Wells, AgResearch, Ruakura
part Chapter 4
•
John Pickering, Veterinarian, Whanganui
part Chapter 5
•
Dorian Garrick, Massey University
part Chapter 6
•
Kevin Stafford, Massey University
Chapter 7
Editorial team:
Duncan Smeaton, Andy Bray, John Meban, Steve Morris, John Journeaux,
Peter Packard, Russell Priest
Printed by: Fusion Print Group Limited, Hamilton
Copyright © NZ Beef Council
Preface
Professor Steve Morris from Massey University and Beef Production Scientist from
AgResearch, Duncan Smeaton, have, in this book, put together what could be rightfully
considered the New Zealand Manual for Beef Cow farming. So complete, thorough and
practical is it that both experienced farmers and new farmers embarking on the bovine
trail will find it as a guiding gospel, complete in its wisdom and forthright in the knowledge
it contains.
Until lately the beef cow has been unable to show just how valuable and profitable she
truly is. Devoted farmers of beef cows of all breeds have known by good old “seat of your
pants” farming that these Queens of the hills have been an integral part of the overall
profitability of their farms. It has been largely due to the eight Beef Focus Farms, in a
project financed by Meat and Wool New Zealand, and the work of the facilitator Duncan
Smeaton and his group of scientists from AgResearch, that we now have figures to prove
just how well farmed cows and the relevant backup cattle, have guarded and increased
the profit of sheep and other stock classes that farm with them. They often do this by
eating some of the best feed available, but more often eating the very worst feed
available too.
The ongoing desire to eat better tasting beef here in New Zealand and supply a better
tasting product to our customers abroad will continually require our beef farmers to have
expectations of both stock and land that will be hard to fulfil. Confidence that what they
are doing is both technically and financially sound will be a big part in achieving this, and
Steve and Duncan and their teams have surely provided a very important footing.
The New Zealand Beef Council had no hesitation in helping sponsor the publication of
this book as an effort in overcoming the somewhat alarming decline in beef cow numbers
being farmed in New Zealand. Although at the time we were not in complete knowledge
of all the data that the focus farms were producing, we felt that as beef cows were the
lynch-pin of the prime beef industry they needed some up-to-date reference material for
use by many sections of the farming industry as well as a reference for teaching.
As with most agricultural sciences in the modern world, beef breeding is a moving target
and improvements and refinements come upon us at a sometimes alarming rate. I’m sure
that before too long some of the methods referred to here will have been updated and
brought into line with what-ever edict is coming down the pipe. I am equally sure that the
vast amount of learning this publication has to offer can be relied upon as sound science
for many years to come.
John Wauchop, Chairman, NZ Sheep and Beef Council and Meat & Wool New Zealand.
January 2009
Note to Readers:
There are 2 condition score (CS) systems in place for recording beef cow body condition or
fat cover. One system operates on a 0 (emaciated) to 5 (fat) scale, the other system
operates on a 1 (emaciated) to 10 (fat) scale. The systems are described in the book.
Whenever CS is discussed in the book, the value for the first system is noted, followed by
the value for the second system in brackets. For example, CS 2.0 (4).
i
Table of Contents
Chapter 1: Introduction ......................................................................................................... 1
Summary ........................................................................................................................... 1
1.1.
The importance of the breeding cow to the beef industry ....................................... 2
1.2.
Beef breeding cow herds ...................................................................................... 4
1.3.
Breeding cows versus other sheep/beef enterprises ............................................. 7
1.3.1
Key points ........................................................................................................ 7
1.3.2
High vs. average performance cows ................................................................. 7
1.3.3
Simplistic calculation of enterprise biological and gross margin performance .... 8
1.3.4
Calculating the full value of breeding cows on sheep and beef farms ................ 9
1.4.
Beef herd sizes ................................................................................................... 13
1.5.
Further reading ................................................................................................... 14
Chapter 2: Weight of calves weaned and cow efficiency ..................................................... 15
Summary ......................................................................................................................... 15
2.1
Introductory comments ....................................................................................... 16
2.2
Setting and achieving calving date and calf weaning weight targets .................... 16
2.3
Optimum cow liveweight and cow efficiency ........................................................ 18
2.4
Genetic selection for cow efficiency .................................................................... 19
2.5
Other pathways to cow efficiency ........................................................................ 21
2.6
Cow liveweight and pasture damage ................................................................... 21
2.7
Weaning date, calf age at weaning ..................................................................... 22
2.8
Further reading ................................................................................................... 23
Chapter 3: Feeding beef cattle............................................................................................ 24
Summary ......................................................................................................................... 24
3.1
Introduction ........................................................................................................ 25
3.2
Energy requirements of cattle ............................................................................. 25
3.2.1
Requirements for maintenance ....................................................................... 26
3.2.2
Requirements for pregnancy........................................................................... 27
3.2.3
Requirements for lactation and calf growth ..................................................... 28
3.2.4
Liveweight loss or gain ................................................................................... 29
3.3
Calculating feed requirements ............................................................................ 30
3.4
Management and nutrition of the beef cow .......................................................... 31
3.4.1
General comments ......................................................................................... 31
3.4.2
Post-weaning (weaning through to 4-6 weeks pre-calving) .............................. 31
3.4.3
Pre-calving (from 4-6 weeks pre-calving to calving) ........................................ 32
3.4.4
Calving to mating............................................................................................ 33
3.4.5
Mating - weaning ............................................................................................ 35
3.5
Matching nutritional requirements to the seasonal pasture supply pattern ........... 35
3.6
Supplementary feeding of beef cows .................................................................. 36
3.7
Assessing the adequacy of feeding ..................................................................... 38
3.8
Condition scoring ................................................................................................ 39
3.9
Further reading ................................................................................................... 41
Chapter 4: Reproduction in the beef cow herd .................................................................... 42
Summary ......................................................................................................................... 42
4.1
Introduction ........................................................................................................ 43
4.2
Potential reproductive rate .................................................................................. 45
4.3
Reproductive management of beef cattle ............................................................ 49
ii
4.3.1
Management and age at first calving of heifers ............................................... 49
4.3.1.1
Critical minimum weight ......................................................................... 52
4.3.1.2
Checklist for successfully mating heifers at 15 months ........................... 52
4.3.2
Time and duration of calving ........................................................................... 53
4.3.3
Age of cow and reproductive performance ...................................................... 54
4.3.4
Calving difficulty (dystocia) ............................................................................. 55
4.3.5
Post-partum anoestrus interval ....................................................................... 58
4.3.6
Bull management ........................................................................................... 60
4.3.7
Pregnancy diagnosis ...................................................................................... 62
4.3.7.1
Two methods of pregnancy diagnosis..................................................... 62
4.4
New reproductive technologies for use in beef breeding cows ............................. 63
4.4.1
Oestrus synchronisation ................................................................................. 64
4.4.2
Artificial insemination (AI) ............................................................................... 64
4.4.3
Producing twin pregnancies ............................................................................ 65
4.4.4
Changing average calf sex ratio...................................................................... 66
4.4.5
Cloning........................................................................................................... 67
4.4.6
DNA parenting................................................................................................ 67
4.5
Further reading ................................................................................................... 68
Chapter 5: Cow health ......................................................................................................... 70
Summary ......................................................................................................................... 70
5.1
Grass staggers (Hypomagnesaemia) .................................................................. 71
5.1.1
Overview ........................................................................................................ 71
5.1.2
Magnesium supplementation .......................................................................... 72
5.2
Facial eczema .................................................................................................... 75
5.3
BVD in beef cattle ............................................................................................... 76
5.3.1
Persistently Infected (PI) animals .................................................................... 76
5.3.2
How does the virus affect cattle? .................................................................... 77
5.3.3
Control of BVD ............................................................................................... 78
5.4
Nitrate poisoning................................................................................................. 79
5.5
Bloat ................................................................................................................... 79
5.5.1
Overveiw ........................................................................................................ 79
5.5.2
Management measures to reduce the risk of bloat .......................................... 80
5.6
Further reading ................................................................................................... 80
Chapter 6: Genetics of calf production from beef cows ........................................................ 81
Summary ......................................................................................................................... 81
6.1
Introduction ........................................................................................................ 82
6.1.1
Selection decisions ......................................................................................... 84
6.2
Selection objectives ............................................................................................ 87
6.2.1
Breeding objectives ........................................................................................ 87
6.2.2
Economic weights and values ......................................................................... 88
6.2.3
The importance of future prices ...................................................................... 88
6.2.4
Selection criteria ............................................................................................. 89
6.3
Estimated Breeding Values (EBVs) ..................................................................... 90
6.3.1
Growth EBVs.................................................................................................. 91
6.3.2
Reproduction EBVs ........................................................................................ 92
6.3.3
Carcass EBVs ................................................................................................ 93
6.3.4
Additional EBVs available ............................................................................... 94
6.3.5
Accuracy of EBVs ........................................................................................... 95
6.3.6
Profitable use of EBVs .................................................................................... 96
6.4
Index Selection (BreedObject) ............................................................................ 97
6.4.1
Angus BreedObject ........................................................................................ 98
6.4.2
Hereford BreedObject ..................................................................................... 99
6.5
Selecting breeding females ............................................................................... 100
6.6
Evidence of genetic progress ............................................................................ 102
iii
6.7
6.8
6.9
6.9.1
6.9.2
6.9.3
6.9.4
6.9.5
6.10
Choice of breed ................................................................................................ 103
Breeding systems ............................................................................................. 107
Crossbreeding .................................................................................................. 108
Alternative crossbreeding systems................................................................ 109
Composite breeds ........................................................................................ 112
Alternating breeds over time ......................................................................... 112
Benefits of crossbreeding ............................................................................. 112
Disadvantages of crossbreeding ................................................................... 113
Further reading ................................................................................................. 114
Chapter 7: Beef cattle handling and yarding ..................................................................... 116
Summary ....................................................................................................................... 116
7.1
Introduction ...................................................................................................... 116
7.2
Cattle handling: Moving cattle .......................................................................... 117
7.3
Working in yards ............................................................................................... 118
7.4
Using forcing pens ............................................................................................ 119
7.5
Working in races ............................................................................................... 120
7.6
Yard design ...................................................................................................... 121
7.7
Conclusions ...................................................................................................... 122
7.8
Further reading ................................................................................................. 122
Appendix 1: Condition scoring (CS) for beef cows ............................................................ 123
Appendix 2: Nutrient composition of commonly available feeds for cattle and sheep ......... 128
1
Chapter 1: Introduction
Summary
The beef cattle industry in New Zealand is made up of 4.3 million cattle of which
1.13 million (2008) are breeding cows. Traditionally, the New Zealand beef herd has been
based upon calves produced by breeding cows. An alternative system involves purchasing
4-day-old calves from the dairy herd and raising these as bulls or sometimes steers for
slaughter, or as replacement heifers in the beef breeding herd.
Achievable production objectives for a commercial beef breeding cow herd are to:
•
Rear to weaning 90-95 calves per 100 cows mated each year for 63 days or less
•
Grow suckling calves at greater than 1.0 kg/head/day
•
Maintain a low death rate in the cow herd (2 to 3% per annum)
•
Use the breeding cow herd to promote and maintain pastures.
At an assumed national average calving percentage (calves weaned/cows mated) of 80%,
the beef cow requires around 16 kg of dry matter per kg of calf weaned. The average beef
cow produces 0.30 kg calf weaned/kg cow weaning weight. In contrast, a high performing
cow produces 0.48 kg calf weaned/kg cow weaning weight (calculated as a 450 kg cow
weaning 92% calves per cow mated, with calves growing at 1.1 kg/calf/day for 180 days)
and is more profitable. Very few farmers get all the components of high cow productivity
right all the time. Clearly it is a difficult business.
Breeding cows are often seen as being less profitable than other stock but this usually
excludes the effects of the beef cow on pasture quality. Recent results have shown that for
much of the year, many breeding cows consume poor quality herbage which is of little or no
value to other stock classes. On this poor quality feed, cows are more profitable than other
live stock classes. Other benefits include lower labour requirements. The cow needs to
play a complementary rather than competitive role to maximise these extra benefits. If a
farm produces only high quality pasture, then the pasture management benefits from cows
are likely to be low.
Profitable Farming of Beef Cows
Chapter 1: Introduction
2
Beef herd sizes are highly skewed because many small holdings (lifestyle blocks) run just a
few beef cattle. About 45% of beef cattle farms have less than 50 cattle and account for
only 7% of total beef cattle. At the other extreme, 6% of farms have over 500 beef cattle.
In aggregate, these farms hold 41% of the total beef cattle.
1.1. The importance of the breeding cow to the beef industry
The beef cattle industry in New Zealand is based on a national herd of around 4.3 million
cattle. Considerable variation in the size of the national beef herd has occurred over the last
two decades.
Beef cattle numbers peaked at 6.3 million in 1975 then subsequently
declined to 4.5 million in 1983.
Currently (2008) the national beef breeding cow herd
numbers 1.13 million.
In New Zealand beef cattle and sheep are usually farmed together, and are complementary
to one another especially under hill country conditions. It is relatively easy for producers to
alter their mix of sheep and cattle to suit current economic conditions and preferences. The
main driving force behind this substitution is the relative profitability between cattle and
sheep. Growth in beef cattle numbers has occurred since 1983 but numbers today are
relatively static at around 4.5 to 5.0 million with fluctuation being mainly due to changes in
the number of dairy and dairy beef cross calves reared for beef production.
Traditionally, the New Zealand beef herd has been based upon the beef breeding cow
producing calves. Normally bull calves are castrated and raised as steers for slaughter
either on breeding or finishing farms. The latter are usually located on better class country.
Heifer calves replace the old and cull cows within the breeding herd and those that fail to
get pregnant. While this management system is practised around the country an alternative
system using calves from the dairy herd has come into prominence. Four-day-old calves
are purchased from the dairy herd and raised as bulls or sometimes steers for slaughter.
Beef breed x Friesian heifers are raised for replacements in the beef breeding herd. The
advantages for the bull system are two-fold. Firstly, there is no capital overhead tied up in a
beef-breeding herd, so more capital can be used for direct income generation. Secondly,
relatively more feed goes into production than maintenance, making this system more
efficient. Needless to say, some traditional beef cow herds are also very efficient.
Profitable Farming of Beef Cows
Chapter 1: Introduction
3
During the spring of the 2006 season the number of dairy calf retentions for beef production
was estimated at around 529,000, equivalent to around 38% of the total calves entering the
beef herd.
With an increasing percentage of the New Zealand beef herd being derived from the dairy
herd, the ratio of beef breeding cows and heifers in the national herd has declined from
36% in 1972-1973 to 27% in 2007-2008 with a resultant increase in “trading” or finishing
stock (see Table 1.1 where they are classified as “other cattle”). Unless retention of female
beef stock numbers increases, future growth and annual fluctuations in beef cattle numbers
will primarily be due to the number of dairy calves originating from the dairy industry that
are reared for beef production.
Another likely reason for the decline in breeding cow numbers is due to their perceived
poorer profitability. On a gross margin / kg DM basis, they are less profitable, but this
excludes the effects of the beef cow on pasture quality.
In fact, the breeding cow is
significantly more profitable than other stock classes on poor quality feed. The cow needs
to play a complementary rather than competitive role to maximise these extra benefits.
About 78% of New Zealand’s beef herd is located in the North Island. While relatively
evenly distributed throughout the North Island, the Northland//Waikato/Bay of Plenty region
has 35% of the total herd. Table 1.2 lists the major beef cattle producing regions. A recent
change in cattle numbers is occurring in the lower part of the South Island where
substantial numbers of dairy beef calves are now being sourced from the increasing
number of dairy farms in the region.
Profitable Farming of Beef Cows
Chapter 1: Introduction
4
Table 1.1:
Composition of the New Zealand beef herd (000) (as at 30 June).
Year
1973
1993
2008
Total Beef Herd
5,343
4,676
4,253
Breeding Cows
1,907
1,419
1,126
Other Cattle
3,436
3,257
3,127
Breeding cows as
36
30
27
% of total
Source: Meat & Wool New Zealand Economic Service.
Table 1.2:
Beef cattle numbers by local region (as at 30 June 2008)
Region
Number of Beef Cattle (000)
% of Total Cattle
Northland/Waikato/BOP
1,489
35
East Coast
1,060
25
509
12
NORTH ISLAND
3,058
72
SOUTH ISLAND
1,196
28
NEW ZEALAND
4,253
100
Taranaki/Manawatu
Source: Meat & Wool New Zealand Economic Service, paper P08031 25 July 2008.
1.2. Beef breeding cow herds
The breeding cow herd is dominated by two breeds, the Angus and Hereford. The heavier
European breeds began to be imported in the late 1960's and some, especially Simmental,
Charolais, South Devon and Limousin have made an impact as terminal sires, where, with
rare exceptions all progeny (both male and female) are sold for slaughter or to finishing
farms.
There has also been an increased use of beef x dairy breeding cows to take
advantage of Friesian genes for higher milk and beef production. It is estimated (2007) that
the national herd consists of 23% Angus, 11% Hereford and 11% Hereford x Angus. Angus
and Hereford crosses would also contribute to a group classified as mixed crosses (36%)
while Friesian cross (12%) and others (7%) make up the rest (derived from data from
Meat & Wool New Zealand Economic Service).
Profitable Farming of Beef Cows
Chapter 1: Introduction
5
Achievable objectives for a commercial beef breeding cow herd are to:
•
Rear to weaning 90-95 calves per 100 cows mated each year for 63 days or less
•
Grow suckling calves at greater than 1.0 kg/head/day
•
Maintain a low death rate in the cow herd (2 to 3% per annum)
•
Use the breeding cow to promote and maintain pasture quality
The national average calving rate (the number of calves weaned as a % of cows mated) is
82% (range 79% to 86%) and has remained at this level for the last 35 years. Age of first
calving is usually 3 years although approximately 30% of all heifer replacements now calve
at 2 years of age. The top third of herds in any year have an average 90% calving rate or
better. There is potential for increased reproductive performance of the beef herd within the
constraint of a natural ovulation rate of 1.0 in cattle.
Because the overall output of a breeding cow herd is dependent on both weaning
percentage and weaning weight of the calf, these are often combined into a term called cow
productivity.
no. of calves weaned x Av. weaning weight
no. of cows joined with bull
Productivity =
However, the total feed consumed by large cows is greater than that of small cows. To
take account of this the term weight of calf weaned per cow joined (i.e. the productivity)
divided by the cow liveweight (usually autumn or weaning weight but some farmers prefer
to use winter liveweight) is a commonly used measure of biological efficiency in the beef
breeding cow herd.
Efficiency =
Productivity
Cow liveweight
As a general rule, smaller cows that wean heavy calves (in excess of 50% of their dam
autumn liveweight) are more efficient. This is probably easier to achieve with some form of
crossbreeding where a larger terminal sire breed is crossed with a smaller dam breed.
The difference in annual feed consumption (kg dry matter/head/year) for three different cow
liveweight types (small, medium and large) means small cows rearing small calves can be
just as efficient and profitable as large cows rearing large calves. Table 1.3 illustrates that
there are a range of cow types that can give similar productivity and returns. If each of the
cows in Table 1.3 rears 50% of their own autumn liveweight to sale as weaner calves they
Profitable Farming of Beef Cows
Chapter 1: Introduction
6
are then all equal in terms of $ return per kg of feed eaten or per stock unit. It is high
productivity irrespective of cow size that makes a beef cow herd profitable
Table 1.3:
Seasonal liveweights and production data for three different beef breeding
cow types and calculations of efficiency and profitability (note liveweights exclude the
weight of conceptus). The calculations assume that small vs. large weaners are worth the
same per kg liveweight.
Small
Medium
Large
Weaning (kg)
430
470
550
Mid-winter (kg)
380
420
500
Pre-calving (kg)
380
420
500
Mating (kg)
410
450
530
Calf wean wt (kg)
215
235
275
2880
3131
3657
100
92
79
80
73.6
63.2
16.7
16.8
16.6
0.186
0.187
0.187
105
107
108
Feed eaten per cow (kg DM)
Number of cows
Number of calves
(at 80% CW/CM*)
Kg DM/kg Calf weaned
Return/kg feed ($)
Gross margin ($ / SU)
* Calves weaned per cows mated.
If a beef cow herd is not productive then the other benefits of keeping this class of stock
need to be large to compensate (i.e. improved sheep performance). These other benefits
have proven difficult to quantify although recent trial results described below provide more
information.
Profitable Farming of Beef Cows
Chapter 1: Introduction
7
1.3. Breeding cows versus other sheep/beef enterprises
1.3.1
•
Key points
In single enterprise analyses comparing profitability of breeding cows, finishing
cattle and breeding ewes, breeding cows usually appear less profitable. However,
this analysis does not take into account the other benefits cows may provide within
the farm system.
•
Cows can play a valuable complementary role in managing pasture quality on sheep
and beef farms but this is difficult to value. Results from the recently completed
Meat & Wool New Zealand Beef Focus Farm project have shown that for much of
the year, many breeding cows consume poor quality herbage which is of little to no
value to other stock classes. On this poor quality feed, cows are more profitable
than other live stock classes. Other benefits include less labour requirements.
1.3.2
High vs. average performance cows
Accumulated figures for breeding cows on New Zealand hill country farms (Meat & Wool
New Zealand Economic Service) indicate that the average beef cow herd is performing well
below potential in that:
•
80 to 82 calves are weaned per 100 cows mated
•
Calves grow at a little over 0.8 kg per day from birth to weaning (accurate figures
not available)
•
0.30 kg calf weaned/kg cow liveweight is produced (calculated as a 500 kg cow
weaning 82% calves per cow mated, with calves growing at 0.90 kg/calf/day for
180 days)
The above implies that one in five cows are non productive, and the pasture these animals
consume therefore represents a lost opportunity. This is partially offset if farmers cull empty
cows at weaning but this has an added cost in terms of higher replacement rates.
Profitable Farming of Beef Cows
Chapter 1: Introduction
8
In contrast, high producing cows in the recent Beef Focus Farm Project funded by
Meat & Wool New Zealand (2008):
•
Weaned in excess of 92 calves per 100 cows mated
•
Grew their calves at 1 to 1.2 kg/head/day from birth to weaning
•
Produced 0.48 kg calf weaned/kg cow weaning weight (calculated as a 450 kg cow
weaning 92% calves per cow mated, with calves growing at 1.1 kg/calf/day for
180 days).
•
Were more profitable (Table 1.4).
High performing cows are often beef x dairy cross cow mated to a terminal sire thereby
taking advantage of hybrid vigour. In this system, all calves are finished for beef, with
replacements sourced from outside the herd.
Trial results indicate that the high levels of performance described above are routinely
achieved on some farms with the cow still carrying out her complementary role of pasture
management, provided the cow can regain any lost weight during the crucial calving to early
mating period. Even so, very few farmers get all the components of high cow productivity
right all the time. Clearly it is a difficult business. The prioritisation of other stock classes
over breeding cows is often the root cause of poor cow performance. Farmers who achieve
high levels of cow performance while using cows for pasture management have learnt the
critical elements that allow these two conflicting goals to be met.
1.3.3
Simplistic
calculation
of
enterprise
biological
and
gross
margin
performance
When various sheep and beef systems are compared on a single enterprise basis, results
such as shown in Table 1.4 can be derived.
Profitable Farming of Beef Cows
Chapter 1: Introduction
9
Table 1.4:
Comparison of four single-enterprise systems modelled using Farmax, each
on the same pasture growth curve.
Average **
performance
cow
High **
performance
cow
High
Fertility
ewe
1yr bull
system
GM* $/ha
449
680
717
796
GM c/kg DM
6.6
8.9
8.6
10.7
Net LWG/ha
350
490
591
908
kg DM/kg LWG
20
16
13
8
* Gross Margin
** As described in section 1.3.2
Average performing beef cows are less productive and profitable than some other
enterprises largely because of their high maintenance requirement and the apparently
non-productive period from weaning to just before calving in terms of product gain/kg DM
eaten. If cows could rear and wean two calves via twin pregnancy that would cause a
quantum leap in productivity and probably profit, but that is mostly outside current
technology. Table 1.4 demonstrates that finishing systems, such as the bull system shown,
are more efficient biologically, and also currently more profitable. High fertility ewes are
also relatively efficient, and are often very competitive financially.
However, the above gross margin analysis can be misleading because it takes no account
of the complementary role that one stock class provides for another within a full farm
system.
1.3.4
Calculating the full value of breeding cows on sheep and beef farms
It is generally recognised that cows play an important role in maintaining pasture quality on
many farms, benefiting other live stock. Cows can also lose a lot of weight during poor
winters, freeing up feed for other less resilient stock. This effect was studied in the recent
Beef Focus Farm Project funded by Meat & Wool New Zealand (2008). On the Northland
farm in this project, cows spent summer, autumn and winter cleaning up behind other live
stock. The quality of the pasture being consumed by the cows was monitored on a monthly
basis for the cows, and for the other stock the cows were complementing. On one of the
Profitable Farming of Beef Cows
Chapter 1: Introduction
10
blocks on the farm, the cows predominantly grazed on medium to steep hill land (with
approximately one quarter of the pasture having a Kikuyu base) and the cows followed
behind ewes and lambs. The other block was rolling to medium hill land with approximately
90% of the pasture Kikuyu based and cows grazed among young cattle.
The grazing residual results showed that the cows were restricted most, during
summer/autumn and early winter, when they were cleaning up behind the other stock
classes (Figure 1.1) but that in spring, they fared much better.
Figure 1.1:
Average post-grazing herbage mass of breeding cows and other stock
classes (Northland Focus Farm).
In general, the quality (MJ ME/kg DM) of pasture offered to the cows was poorer than that
grazed by the other live stock (Figure 1.2). The quality of the diet offered to the cows
changed with season to a greater extent than that of the other live stock classes, reflecting
the ability of management to prioritise better quality feed to other live stock classes during
seasons when poor quality feed was present (summer and autumn). Over the 3 years of
the study, the average metabolisable energy concentration (ME) of pasture consumed by
cows was 8.8 vs. 10.3 MJ ME/kg DM for the other stock classes the cows were
complementing.
Profitable Farming of Beef Cows
Chapter 1: Introduction
11
Figure 1.2:
Average metabolisable energy content of pasture offered to the breeding
cows and other livestock classes.
Cow liveweights and condition score peaked during summer in response to good feed
availability during spring and early summer (Figure 1.3) and declined again during late
summer and autumn. Despite the poor quality of feed and loss in cow liveweight, each year
the calves grew at greater than 0.6 kg/day during the late summer/autumn period and
greater than 0.8 kg/day over the whole lactation period. This demonstrates the ability of the
cow to buffer the calf, through liveweight loss and milk production during this period on poor
quality pasture.
Figure 1.3:
Average cow (conceptus-free) liveweight and condition score (on a 1 – 10
scale).
Observations on a second focus farm in the same project as reported above, in Southland,
showed similar buffering effects by the cow.
Profitable Farming of Beef Cows
Chapter 1: Introduction
12
If the poor quality herbage is not consumed by cows then it either will be consumed by
another stock classes or it will decay. In the Focus Farm Project, the former option was
tested using the computer models Q-Graze and Farmax (see Further Reading). The weight
gain or loss of 2-year-old bulls fed the same quality of pasture as the cows was calculated.
As with the breeding cows, the 2-year bulls were predicted to gain weight during spring and
early summer and then lose weight during autumn and early winter (Figure 1.4).
Figure 1.4:
Estimated two year bull liveweight gain (kg/head/day) if fed on the same
herbage as the breeding cows on the Northland farm, as calculated by Q-Graze. The
change in value of 2-year bulls ($/head/day) is based on liveweight change and seasonal
store market values.
Total liveweight gain by the bulls for the year was calculated at only 38 kg. The analysis
showed a total annual increase in bull value of $128 per cow equivalent. In contrast, cows
were calculated to be returning $363 per head (after losses). That is, the cows returned a
gross margin income of $235/cow more than the bull equivalent system could have done on
the same feed. A similar exercise on the Southland farm showed a similar result.
No one would normally farm finishing animals in the way shown above, but it does illustrate
the fact that the pasture that the cows are consuming has very little value to other live stock
classes for a large portion of the year. In fact there are times when this herbage could be
considered a liability rather than an asset.
Profitable Farming of Beef Cows
Chapter 1: Introduction
13
If a farm produces only high quality pasture, (though intensive subdivision etc) then the
above benefits due to running cows are likely to be much less and returns will be closer to
the enterprise results in Table 1.4. In this situation, cows should be replaced by higher
return stock classes. However, it should be noted that intensive subdivision is not feasible
on many hill country farms.
1.4. Beef herd sizes
Beef herd sizes are highly skewed because of the many small holdings (lifestyle blocks)
which run a few beef cattle. Figure 1.5 shows that small holdings make up the majority of
farms with beef cattle. However, these small holdings have a relatively small proportion of
the total beef herd. For example, 22% of the beef holdings have less than 10 beef cattle.
In aggregate, these holdings have just over 1% of the total beef cattle. About 45% of beef
cattle farms have less than 50 cattle and account for only 7% of total cattle. This group of
farms are likely to be less responsive to industry conditions than the larger more
commercial farms.
At the other extreme, 6% of farms have over 500 beef cattle.
In
aggregate, these farms have 41% of the total beef cattle.
Figure 1.5:
Beef cattle herd size distribution by % of cattle and % of farms, June 2002
Source: Statistics New Zealand (2002) Agricultural Production Census – Note that this is
the most recent information available.
Profitable Farming of Beef Cows
Chapter 1: Introduction
14
1.5. Further reading
AgResearch. 2002. In “Pasture quality: Principles and management, The Q Graze Manual.
A reference document to accompany The Meat New Zealand pasture quality
workshops, Published January 2002 Meat New Zealand, PO Box 121, Wellington,
pp 1-26.
Farmax. A decision support model for livestock farms. www.farmax.co.nz
Marshall, P.R.; McCall, D.G.; Johns, K.L. 1991. Stockpol: A decision support model for
livestock farms. Proceedings of the New Zealand Grasslands Association. 53:
137-140.
Meat & Wool New Zealand Economic Service.
Various reports, available on
www.meatandwoolnz.com
Smeaton, D.C.
2003.
Profitable Beef Production.
A guide to beef production in
New Zealand. Published by the New Zealand Beef Council. ISBN: 0-473-09533.5.
Smeaton, D.C.; Boom, C.J.; Archer, J.A.; Litherland, A.J. 2008. Beef cow performance and
profitability. Proceedings of the 38th seminar of the Society of Sheep and Beef
Cattle Veterinarians NZVA, pp 131- 140.
Profitable Farming of Beef Cows
Chapter 1: Introduction
15
Chapter 2: Weight of calves weaned and cow efficiency
Summary
The total weight of calves weaned is the key production output of the breeding cow herd
and is the end result of many input factors. About 70% of the variation in weaning weight of
calves is due to differences in milk production of the dam. To achieve high calf weaning
weights cows must be well fed before and after calving. A high level of feeding after calving
is also necessary for a high conception rate at rebreeding. Date of weaning should depend
on feed supply.
The best cow for hill country is a medium sized cow that weans a high proportion of its
liveweight in calf weaning weight. The optimum liveweight of mixed-age Hereford x Friesian
cows is estimated to be 430 to 450 kg at mating. In a trial, cows at optimum weights, and
rearing a live calf, weaned calves at 180 days of age that were 52% of their mother’s
liveweight at mating. Including losses due to empty cows and calving losses, the ratio
dropped to 44%. The average rate of calves weaned per cow mated in this case was 82%.
Selecting to improve the efficiency of feed conversion in a cow herd has been proposed as
an alternative to selecting for growth rate.
Feed conversion ratio is a measure of the
amount of feed eaten per unit of bodyweight gain or carcass weight gain.
Net feed
efficiency refers to variation in feed intake between animals beyond that related to
differences in growth and liveweight. Selection for this should reduce herd feed costs.
Ranking animals on net feed efficiency requires measuring differences in their feed intake,
liveweight and growth rate over a defined test period.
Selecting cows for lifetime productivity at first weaning can be advantageous but requires
tagging of calves with their birth mothers. The process is complex, but the gains are there if
farmers are willing to invest the time.
Efforts have been made to improve cow productivity through multiple suckling via one
means or other, but commercial success remains elusive because of technical and
biological limitations. In the meantime, the best objectives are to run cows at optimum
weights, take maximum advantage of their ability to gain and lose weight to support milk
production and to maintain pasture quality, achieve high pregnancy rates and survival and
take maximum advantage of genetic opportunities and hybrid vigour.
Profitable Farming of Beef Cows
Chapter 2: Weight of calves weaned and cow efficiency
16
2.1
Introductory comments
The total weight of calves weaned by the herd is a key production output of the
breeding cow herd.
It is a reflection of:
•
Reproductive success; clearly, empty cows do not wean a calf
•
Feeding levels of cow and suckled calf
•
Cow and calf genetics, hybrid vigour
•
Cow and calf health
•
Age at weaning (for comparative purposes, a standardised weaning age of 180 days
is often used).
The weaning weight of an individual calf from a cow is dependent on the above factors and
also more specifically:
•
Cow milk production (in turn dependent on numerous factors)
•
Age of dam
•
Age of calf at weaning, affected in turn by:
•
Calving date
All the above are discussed in the various chapters of this book.
The material below
discusses management aspects of integrating these factors.
2.2
Setting and achieving calving date and calf weaning weight targets
The ability to wean heavy calves has become progressively more important in conventional
single-suckled breeding-herds because of the trend towards selling cattle for slaughter at a
younger age. This means that growth to weaning represents a higher proportion of total
growth to slaughter.
Calf weaning weight targets will be specific to the farm in question but a minimum liveweight
gain target for a suckled calf on hill country should be 1.0 kg/calf/day.
Typically in
New Zealand it is less than this, particularly if the cow is expected to do a lot of pasture
quality management work. Most beef calves are weaned at around 5 to 7 months of age
resulting in calf weaning weights in the range of 180 to 240 kg (assuming a 35 kg birth
weight).
Some farmers achieve weights of up to 280 kg/calf.
The importance of a
condensed calving (target of 70% of cows calving in the first 21 days of calving) within an
Profitable Farming of Beef Cows
Chapter 2: Weight of calves weaned and cow efficiency
17
appropriate calving period (where the planned start of calving is synchronised with pasture
supply) cannot be underestimated because of its effect on calf weaning weight and cow rebreeding performance. Many commercial beef herds calve too early in the spring. The
usual sign for this is a slow start to calving (less than 50% calved in the first 21 days of
calving) which compromises calf weaning weights and cow rebreeding performance.
The rate of growth of the suckling calf largely depends on the cow’s milk supply, which in
turn depends on the food available to the cow. Some research suggests that about 70% of
the variation in weaning weight of calves is due to differences in milk production of the dam.
A calf can consume 10-15% of its liveweight as milk each day. A 50 kg calf can drink 7-8 kg
milk per day and at this rate will grow at 1.0 kg liveweight gain/day. As the calf grows, its
capacity to drink milk increases and there are obvious advantages if the cow can increase
her milk production to match this demand. A calf at 120 days weighing 150 kg could
consume around 15 kg of milk. It is highly unlikely a cow would produce that much milk at
that stage and so the calf gets its extra nutrients by consuming pasture.
To achieve high calf weaning weights, cows must be well fed before and after calving. A
high level of feeding after calving is also necessary for a high conception rate at rebreeding.
Experience suggests that a feed budget should allow for a cow to eat in excess of 12 kg
DM/day from the day of calving. How this will be achieved depends on the date of calving,
and may require feed saved from late winter. Cows will often buffer their calves against
underfeeding in early lactation by losing liveweight to maintain calf growth. However, this
can not happen in poor conditioned cows (CS 2 (4) or less), so it is therefore desirable to
have cows in a condition score of 2.5 (5) or better at calving. A recent trial at Massey
University indicated that for heifers, a sward (pasture) height of 6 cm is sufficient in the first
month after calving increasing to 10-12 cm during the second month.
Date of weaning should depend on feed supply (it often depends on labour availability and
sale date). If there is ample feed, there is little to be gained from early weaning unless there
is an opportunity to use the cows in a mob for pasture control or preparation for other
classes of stock. However, if hill country pastures dry out badly in summer, calves could be
weaned and put onto what fresh pasture is available and the cows fed hard rations to
relieve grazing competition.
Profitable Farming of Beef Cows
Chapter 2: Weight of calves weaned and cow efficiency
18
2.3
Optimum cow liveweight and cow efficiency
The best cow for hill country is a medium sized cow that weans a high proportion of its
liveweight in calf weaning weight. The cow needs to be in good condition at weaning so
she can then use her excess body condition as “supplementary feed” over the winter
months. In fact, cows should be at their maximum liveweight and condition at weaning
indicating they have eaten as much as possible of the excess spring-summer feed that
usually occurs on hill country properties.
It is possible for cows to wean calves (at 180 days age) that weigh 50% to 60% of the cow’s
weight (compared to 35% to 45% on average). This is neither a new objective nor is it easy
to achieve. In a project at Whatawhata Research Centre (Smeaton and others 2000) the
optimum liveweight of mixed-age Hereford x Friesian cows was estimated to be 430 to
450 kg (Figure 2.1).
Anecdotally, many farmers run their cows at weights significantly
heavier than this, thereby foregoing productivity advantages and running some risk of
surplus fat in the udder which can jeopardise milk production (especially in heifers). At
optimum weights in the Whatawhata project, cows rearing a live calf weaned calves at 180
days of age that were 52% of their mother’s liveweight at mating. Including losses due to
empty cows and calving losses, the ratio dropped to 44%. In summary cow productivity is
extremely sensitive to:
•
Cow liveweight relative to calf weaning weight
•
Pregnancy rate
•
Cow survival
•
Calf survival, mostly around the calving period
Figure 2.1:
Illustration of optimum liveweight for Hereford x Friesian breeding cows
Source: Reworked data from Smeaton and others (2000).
Profitable Farming of Beef Cows
Chapter 2: Weight of calves weaned and cow efficiency
19
2.4
Genetic selection for cow efficiency
(other breeding traits are discussed in Chapter 6)
Traditionally, beef producers improve their herds by selecting for growth. Growth is an easy
and economical trait to measure and is moderately heritable. Selection for growth traits has
resulted in faster growing cattle, however it has also resulted in the introduction of some
correlated undesirable traits such as increased birth weights leading to calving difficulties,
delayed sexual maturity and increased herd maintenance requirements associated with the
feed costs of larger animals.
In most beef cattle production systems, researchers have established that 65% to 85% of
total feed intake is required by the breeding cow herd, and that half of the total feed intake is
required just to maintain cow liveweight. The costs of maintaining the breeding cow herd is
clearly an important factor determining the efficiency of beef production.
Despite its economic importance, farmers in New Zealand do not usually assess the cost of
feed for their farming operation. The complementary roles of beef cattle on sheep farms
complicate the economic assessment of feed efficiency in New Zealand’s mixed livestock
farming systems as discussed elsewhere. However, as profitability is a function of both
inputs and outputs, there is a need to consider avenues for reducing inputs in order to
improve efficiency of production and increase profits.
By selecting to improve the efficiency of feed conversion in a herd, the producer can strive
to improve the efficiency of converting feed to gain, rather than concentrating on growth
alone. Different measures of the efficiency of growth have evolved over the years because
of the complex nature of feed use in the animal. The most commonly used definitions to
describe the efficiency of growth are:
Feed Conversion Ratio (FCR)
This is a measure of the amount of feed eaten per unit of bodyweight or carcass weight
gain. Since feed is the numerator, FCR should be minimised. Common values for growing
ruminants grazing pasture are around 7-10 (kg fed consumed / kg liveweight gain) whereas
pigs and poultry aim for values less than 2. The term Feed Conversion Efficiency (FCE) is
also often used but the more correct term is FCR as it is a ratio (i.e. feed eaten per unit of
gain)
Profitable Farming of Beef Cows
Chapter 2: Weight of calves weaned and cow efficiency
20
Efficiency of Feed Utilisation
Efficiency of feed utilisation is simply the reciprocal of FCR.
The important point to
remember is that more efficient cattle will have a lower FCR and a higher efficiency of feed
utilisation. When comparing efficiencies from different studies or farms, calculations need
to clearly state the measures (units) of inputs and outputs used.
Residual Feed Intake
An issue that is of considerable practical interest is the extent to which individual animals
are more or less efficient than would be expected. Animals can be compared using net
feed conversion efficiency or the residual feed intake.
More efficient cattle can
theoretically be found within any desired cattle weight range, and selection will not
necessarily increase mature size.
Net feed efficiency (NFE) refers to variation in feed intake between animals beyond that
related to differences in growth and liveweight. Consequently it is expected that selection
for improved NFE may reduce herd feed costs with little or no adverse changes in growth
performance. Ranking animals on NFE requires measuring differences in their feed intake,
liveweight and growth rate over a defined test period. A high NFE bull will consume less
feed than expected over the test period and have a lower (negative) net feed intake. A low
NFE bull will consume more feed than expected over the test period and have a higher
(positive) net feed intake. An animal’s expected feed intake is predicted from the test
groups’ average feed requirements for a particular growth (say 1 kg/head/day) and
liveweight (say 300 kg). An animal’s net feed intake is simply the difference between its
predicted feed intake and its actual feed intake.
Selecting for efficient cows within a herd (usually when the first calf is weaned)
Calf weaning weight, adjusted for calf sex, calf sire breed and year-of-birth of dam, has a
moderate repeatability as a dam trait1 of 0.37 (if adjusted for date of birth of calf), or 0.29 (if
unadjusted for date of birth). Both of these traits, again as dam traits, are heritable, and the
New Zealand heritability estimates were 0.26 and 0.19, respectively (Morris and others
1993). Cow weights, adjusted for age, or year of birth, are highly repeatable (0.54), and
moderately heritable (0.26).
1
Trait: A measured genetic feature or characteristic
Profitable Farming of Beef Cows
Chapter 2: Weight of calves weaned and cow efficiency
21
Selecting cows for a productivity objective is probably best achieved by using a linear index
of calf weight and cow weight (e.g. A x calf weight difference from the adjusted mean, minus
B x cow weight difference from the adjusted mean), rather than by using a ratio of the two
adjusted weights. It is acknowledged that tagging and some recording is required, to get
the best out of this procedure (i.e. calf-to-dam links, calf sex, date of birth), and if done on a
commercial property, comparisons would need to be done within cow breeds or breed
crosses, because of differing amounts of hybrid vigour expected.
Managing separate
grazing groups around or after calving may also complicate interpretation of the results.
It is also important to remember that the sire contributes to herd productivity, i.e. the sire of
the calf and also the sire of the cow. The Breeding Values of candidate sires need to be
taken into account when purchasing service sires and when breeding/purchasing heifer
replacements. The above process is rather complex, but the gains are there if farmers are
willing to invest the time and the recording costs.
2.5
Other pathways to cow efficiency
Various efforts have been made to improve cow productivity either via twinning or by using
embryo transfer to put high growth rate calf genetics into small, high milk producing cows,
but commercial success remains elusive because the technology required remains
immature or inadequate at several stages of the production cycle (see Chapter 4 also).
Therefore, the right system at present would aim to: run cows at optimum weights; take
maximum advantage of their ability to gain and lose weight to support milk production; use
cows to maintain pasture quality; achieve high pregnancy rates and survival; and take
maximum advantage of genetic opportunities and hybrid vigour.
2.6
Cow liveweight and pasture damage
Heavy cows are more likely to cause pasture damage and pugging on wet or steep hill
country than light animals. In wet weather on steep hill country, damage can be severe,
increasing the risk of erosion and weed invasion although this problem is manageable with
care. This is not discussed in detail here (see Further Reading for more information).
Profitable Farming of Beef Cows
Chapter 2: Weight of calves weaned and cow efficiency
22
2.7
Weaning date, calf age at weaning
The main advantage of early weaning appears to be in retaining cow body condition. If the
previous management has been correct, this should not be an important issue. However in
case of droughts, and a requirement to graze cows off the farm as part of the drought
management strategy, early weaning can be practiced.
Weaning time is often determined by managerial convenience and timing of weaner sale
dates in the district. Farmers often like to wean on the day of these sales so calves are
trucked to the sale straight off their mothers looking in their best condition. However, if
calves are not being sold at weaning, then weaning date can be related to feed supplies. In
one recent study (Figure 2.2), calves weaned late (9 months of age) had a significant live
weight advantage (55 kg) over calves that were weaned at the normal time (6 months of
age). Most of this advantage was retained through to 18 months of age. This advantage in
weight gain was shown to be due to milk intake. This study also demonstrated that weaned
calves are more susceptible to internal parasites than calves that are still receiving milk.
Figure 2.2:
Mean calf liveweights for calves weaned at normal time (20 March), late
weaned (26 June), or late weaned with no suckling from 20 March on.
Source: Boom and others (2003).
Profitable Farming of Beef Cows
Chapter 2: Weight of calves weaned and cow efficiency
23
2.8
Further reading
Boom, C.J.; Sheath, G.W.; Vlassoff, A. 2003. Interaction of gastro-intestinal nematodes
and calf weaning management on beef cattle growth. Proceedings of the
New Zealand Society of Animal Production 63: 61-65.
Thorrold, B. 2008. Management to minimise environmental damage, Ch 10 In Profitable
beef production, A guide to beef production in New Zealand.
D.C. Smeaton.
A book, Ed
Published by Meat & Wool New Zealand, Beef Council. Third
Edition. Meat & Wool New Zealand, PO Box 121, Wellington.
Smeaton, D.C.; Bown, M.D.; Clayton, J.B. 2000. Optimum liveweight, feed intake,
reproduction, and calf output in beef cows on North Island hill country,
New Zealand. New Zealand Journal of Agricultural Research. 43: 71 - 82.
Smeaton, D.C.; Harris, B.L.; Xu, Z.Z.; Vivanco, W.H. 2003. Factors affecting commercial
application of embryo technologies in New Zealand: a modelling approach.
Theriogenology. 59: 617-634.
Profitable Farming of Beef Cows
Chapter 2: Weight of calves weaned and cow efficiency
24
Chapter 3: Feeding beef cattle
Summary
This chapter describes the feed and grazing management requirements of breeding cows.
Beef cattle should be fed at levels appropriate to their production target and the long term
sustainability of the farming enterprise. Due to the variability of pasture growth and the
demands of other livestock classes, it is rare for a farmer to get feed allocation absolutely
correct.
In calculating feed requirements for cattle, the requirement for maintenance,
liveweight gain, milk production, and pregnancy are estimated separately and then added
together. Requirements for cattle, based on these metabolic processes are provided. In
practice many people calculate metabolisable energy (ME) feed requirements from feed
tables or unwittingly by using farm management models that calculate intake as part of
modelling their farm systems.
The feed management strategy for a beef cow-breeding herd is determined by a balance of
feed supply patterns, competing resources and market requirements. There are major
benefits from running beef cows on hill country farms because of their flexible feed demand
which can be aligned with the seasonal pasture growth curve. An additional benefit is their
ability to assist in the management of pasture quality. An important attribute of the hill
country beef cow is her ability to transfer feed from the late spring/summer period to winter
via stored body fat.
If this is managed successfully, it is often unnecessary to feed
supplements to cows.
For simplicity the annual nutritional requirements of spring calving beef cows are divided
into the following periods: Post-weaning; Pre-calving; Post-calving; Post-mating.
Both
liveweight and body condition scoring are useful aids to checking the feeding and
management of the herd at critical periods of the yearly production cycle.
Condition
scoring, seemingly less precise than weighing, is a practical way of monitoring the animals.
The main management decision that affects the matching of the cow’s needs to pasture
production is the time of calving. Since most of New Zealand’s beef cows are run on farms
where sheep contribute the majority of stock numbers, the time of calving will also be
influenced by the needs of other stock classes, usually lambing ewes.
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
25
3.1
Introduction
Beef cattle should be fed at levels appropriate to their production target and the long term
sustainability of the farming enterprise. Due to the variability of pasture growth and the
demands of other livestock classes, it is rare for a farmer to get feed allocation absolutely
correct. Pasture growth rate predictions can differ from actual because of variable climatic
conditions. Forage crops other than pasture are not used widely, but supplementary feed of
various types (hay, silage, concentrates) may be used in times of feed shortage during
winter or dry summers.
The management on sheep and beef cattle farms ranges across the spectrum from
extensive, where conservative stocking rates are used and the animal’s body weight acts as
the main buffer between pasture production and feed requirements, through to intensively
managed and planned systems where the farmer makes decisions on a daily basis to
achieve this balance. In the more intensive systems, management to increase animal
production is focused on lambing and calving liveweight targets, weaning date, flushing, and
the timing of the sale of store lambs, weaners, cull ewes, cull cows and finishing steers or
bulls.
The points made above highlight the fact that most beef production is in conjunction with
other livestock classes. When evaluating a beef cattle operation consideration must always
be given to what other stock classes the cattle are complementing or competing against at
various times of the year, and how their performance will change if the beef system is
changed.
3.2
Energy requirements of cattle
Feed requirements represent the amount of feed which must be consumed in order to
sustain a defined level of production. For any specified level of performance
(e.g. pregnancy, liveweight gain or milk production), sufficient nutrients and energy must be
supplied to the animal tissues to meet metabolic demands. Requirements can be
conveniently expressed as metabolisable energy (ME) because with most pastures, energy
is the most limiting factor for a given level of production. Other nutrients such as protein,
minerals and vitamins (except where there is a known deficiency) are almost always
present in adequate amounts. However, in some instances e.g. young growing animals,
protein may be limiting, especially on low digestible mature type pastures.
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
26
The major determinants of the energy requirement of grazing livestock are:
•
liveweight and body condition
•
stage of pregnancy
•
level of milk production
•
rate of liveweight gain or loss
•
composition of liveweight gain or loss
•
level of activity in eating and movement
•
possible effects of climate
•
sex of animal
•
walking distance and climbing hills
Obviously it is difficult to include all these variables in tables of ME requirements that are
easy to use. In calculating feed requirements for cattle, the requirements for maintenance,
liveweight gain, milk production, and pregnancy are estimated separately and then added
together. The energy requirements of growing cattle are not covered here. Refer instead to
the Further Reading section (Nicol and Brookes, 2007; Smeaton 2007).
3.2.1
Requirements for maintenance
The ME requirement for maintenance is the amount of ME that must be supplied to provide
energy needed for essential body functions. If this energy is not supplied in the diet it must
be obtained by mobilising body tissue, predominantly fat.
As liveweight increases, so too does maintenance energy requirement (Table 3.1), with
every 100kg increase in liveweight requiring an additional 11 MJ ME/day.
grazing and activity costs on hard hill country are significant.
Increased
These maintenance
requirements are significantly higher than those used by Geenty and Rattray (1987).
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
27
Table 3.1:
The metabolisable energy requirement (MJ ME/cow/day) for maintenance of
beef cows. Source: Nicol and Brookes (2007).
Liveweight (kg)
Land class
300
400
500
600
Easy hill
-
55
66
77
Hard hill
50
65
75
-
Notes:
Add/subtract 7% per MJ ME for diets below/above 10.5 MJ ME/kg DM.
Add 15% for adult bulls.
A guideline requirement for maintenance can be given as:
0.62 MJ ME/kg liveweight 0.75 for cows on easy hill country
0.70 MJ ME/kg liveweight 0.75 for cows on hard hill country
3.2.2
Requirements for pregnancy
The amount of energy used for both maintenance and growth of the foetus and the products
of conception depends on:
•
Days from conception. The greatest increase in requirements occur in the last third
of pregnancy
•
Number of offspring (twins rarely exceed 1% of births in beef cattle)
•
Size of the foetus
Guideline requirements for pregnancy for calves of varying birthweights are shown in
Table 3.2. These values are additional to the maintenance requirements of the cow.
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
28
Table 3.2:
The metabolisable energy requirement of beef cows (MJ ME/cow/day) for
pregnancy (in addition to maintenance requirement). Source: Nicol and Brookes (2007).
Calf
birth weight (kg)
-12
Weeks before
Total for
calving
Pregnancy
-8
-4
0
MJ ME/cow/day
MJ ME
30
6
11
20
34
1700
40
9
15
26
45
2300
50
11
18
32
55
2800
Notes:
Add these to the maintenance requirement of the cow.
Adjust proportionately for pregnancy rate of the herd, for example,
Pregnancy rate = 95%, ME for 40 kg birthweight, 4 weeks pre-calving
= 0.95 x 26 = 25 MJ ME/cow/day.
3.2.3
Requirements for lactation and calf growth
The ME requirement for milk production depends on:
•
Total milk yield (litres)
•
Milk composition - because milk varies in concentration of fat, protein and lactose,
the ME requirement per litre will also vary.
It is extremely difficult to know the milk production of beef cows but it will usually range from
5-10 litres/day for single suckled cows. In addition and as a guideline, 5.8 MJ ME/kg milk is
assumed.
The costs of lactation and calf growth (Table 3.3) are estimated as 60 MJ ME/kg calf
weaning weight (slightly less for very light calves). Assumptions have been made about the
proportion of the requirements of the calf which has been supplied by milk and grazing.
However, this ratio does not markedly affect the total ME requirements for calf growth to
weaning.
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
29
Table 3.3:
The metabolisable energy requirements of beef cows and their calves during
lactation (in addition to cow maintenance requirements). Source: Nicol and Brookes (2007).
Calf weaning
weight (kg)
Months after calving
+1
+3
+5
+7
MJ ME/cow + calf/day
Total for
lactation
MJ ME
150
35
45
55
55
8700
200
40
55
65
75
12000
250
50
70
85
95
15000
300
60
80
100
115
18000
Notes:
Add these figures to cow maintenance requirement. (See Table 3.1)
Adjust proportionately for weaning %, for example
85% weaning, 200 kg calves, 5 months = 0.85 x 65 = 55 MJ ME/cow/day.
Add/subtract 8% MJ ME for diets below/above 11.0 MJ ME/kg DM.
3.2.4
Liveweight loss or gain
When animals lose weight, mobilisation of body tissue releases energy which therefore
does not have to be supplied by the diet. In lactating animals, this energy can be used to
maintain milk yield, even though the animal is losing weight. The figure often used for
New Zealand beef cows is 55 MJ ME required per kg of LWG gain, and 1 kg of liveweight
loss in mature cows substitutes for around 30 MJ ME of herbage intake. Thus the net cost
of losing and gaining a kg of liveweight is 25 MJ ME/kg of liveweight.
Condition Score (CS) and liveweight change
Target condition scores are often given for particular stages of the production cycle. When
using the 0 to 5 CS scale, one unit change in CS is equivalent to 75 kg for a 500 kg
Hereford cow. On the 1 to 10 scale, the weight change per unit is about 40 kg
The approximate quantities of ME per 1 unit change of condition score (Scale 0-5) range
from 4815 MJ ME/CS for a non lactating cow of with a CS of 2.0, to 5650 for a non lactating
with a CS of 4. For lactating cows it is 3450 (CS 2.0) and 4500 (CS 5.0) MJ ME/CS
change. These values would be about half for the 1 to 10 scale. Condition scoring is
discussed in more detail later in this chapter.
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
30
3.3
Calculating feed requirements
In practice most people calculate ME feed requirements in computer models without even
realising it. Less commonly, they may estimate them from feed tables such as in Table 3.1
to 3.4. Requirements in kg DM/head/day can be determined from these tables once a value
of the energy (ME) content of feed is known. Pasture typically contains 8 to 12 MJ ME/kg of
DM depending on the quality of pasture. Note that some feed tables are quoted in kg DM.
These should be used with caution when using them for pastures of varying energy content.
Table 3.4 provides an example of how the previous information can be used to compute the
annual metabolisable energy requirements for breeding cows with different levels of
productivity on either good or hard hill country. Note the greater (23%) feed requirements of
the more productive cow in the better environment compared to that of the cow in the hard
hill country.
Table 3.4:
The annual ME requirements of beef cows in hard and easy hill country.
Source: Nicol and Brookes (2007).
Specifications
Hard hill
Liveweight (kg)
Easy hill
400
550
Weight loss/gain (kg total)
30
30
Calves born/cow joined
92
97
Calf birth weight (kg)
30
40
Calves weaned/cow joined
86
90
175
250
Calf weaning weight (kg)
ME requirements (MJ ME)
Maintenance
365 x 65 =
23725
365 x 72 =
26280
30 x 25 =
750
30 x 25 =
750
0.92 x 1700 =
1565
0.97 x 2300 =
2230
0.86 x 10350 =
8900
0.90 x 15000 =
13500
Weight loss/gain
Pregnancy
Lactation and calf growth
Total annual (MJ ME/year)
Notes:
35000
42750
Maintenance requirement from Table 3.1
Net cost of loss and regain of weight is 25 MJ ME/kg (Para 3.2.4).
Total requirement for pregnancy from Table 3.2 and number of calves born (NCB).
Total requirement for lactation and calf growth from Table 3.3 and number of calves weaned
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
31
3.4
Management and nutrition of the beef cow
3.4.1
General comments
The management strategy for a beef cow-breeding herd is determined by a balance of feed
supply patterns, competing resources and market requirements. There are major benefits
from running beef cows on hill country farms because of their flexible feed demand which
can be aligned with the seasonal pasture growth curve. An additional benefit is their ability
to assist in the management of pasture quality. In this respect, they play an important role
on kikuyu pasture in Northland and brown-top dominant swards elsewhere. Hill country
farmers marketing weaners in the autumn will often put in place a strategy to cope with
calving ahead of the spring pasture growth, in order to supply the market with older, and
therefore larger, weaners. Farmers marketing progeny in the following spring or autumn, or
finishing the weaner steers themselves, have the flexibility of being able to calve at a more
appropriate time in relation to their pasture growth curve. An appreciation of the pasture
growth curve of a farm is fundamental to the management of any pasture based production
system. When calving before the spring pasture growth flush, the cow is placed in a more
competitive rather than a complementary position with other livestock classes that might
also be able to utilise that same scarce feed.
For simplicity we can divide the annual nutritional requirements of mature spring calving
cows into the following periods: Post-weaning; Pre-calving; Post-calving; Post-mating. Both
liveweight and body condition scoring are useful aids to checking the feeding and
management of the herd at critical periods of the yearly production cycle.
Condition
scoring, while seemingly less precise than weighing, is nevertheless a practical way of
monitoring the animals.
3.4.2
Post-weaning (weaning through to 4-6 weeks pre-calving)
Weaning of beef calves normally occurs at 5 to 7 months of age. It can be carried out
successfully at 4 months (this can be an appropriate drought management strategy)
provided appropriate provision is made for post-weaning feed for the calf. In the beef cow
calendar this leaves 5 months of the year that beef cows are low priority stock and can
function as 'work horses' eating rank pasture and controlling shrub re-growth provided they
were in good condition at weaning . During this time, priority can be given to other classes
of livestock and cows become one of the few groups available that can be restricted in the
interests of pasture development and utilisation. This is a major justification for maintaining
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
32
a breeding cow herd on hill country. Not only has it significant advantages for the farm as a
whole, but it has in fact been shown to be beneficial for the cows to lose around 10% of
their liveweight in the post-weaning period.
Cows losing that order of liveweight have increased longevity and suffer no reduction in
performance; provided their nutritional requirements are met in the pre- and post-calving
periods and lost liveweight is regained. Cows fatter than condition score (CS) 3.5 (7 on 1 to
10 scale) at calving are more prone to calving difficulties and to metabolic disease. A
reduction in intake around calving should not be carried out too rapidly with fat cows, as
they can suffer from hypomagnesaemia if subjected to sudden severe restrictions in intake.
Some farmers rotationally graze their cows behind the ewes in a winter rotation during this
period. In such situations cow intakes are very low e.g. Angus cows can eat as little as
3-3.5kg DM/day. This highlights their efficiency and supports the theory that an efficiently
managed beef cow could have a true winter stock unit cost of 3.5 stock units compared to
the commonly accepted value of 6 to 7.
Minimising cow feed requirements during
maintenance periods can have a significant impact on overall feed efficiency and therefore
profitability on a hill country sheep and cattle farm. This should be a consideration when
establishing appropriate stock unit equivalents.
3.4.3
Pre-calving (from 4-6 weeks pre-calving to calving)
Cows that have lost in the order of 10% body weight post weaning need to regain some
condition pre-calving and will need to be on a rising plane of nutrition up to and through
mating. If they do not, there is a risk they will be too weak at calving and prone to metabolic
problems, and calf losses can be high (of the order of 10%-20%).
A relatively short period (4 weeks) of high nutrition (6-8kg DM intake/cow/day) is usually
sufficient. Note that the calf is gaining at 250 grams/day in utero during the last month of
pregnancy. If feed is available, liveweight gain on cows will be easier to achieve pre-calving
than during early lactation and is unlikely to have any significant effect on calf birth weights,
except at extremes of feeding levels. If cows calve at CS 2.5-3.0 (5 to 6) it will make the
mating condition target of 3.0 (6) a lot easier to meet.
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
33
While poor pre-calving nutrition and body condition score can exacerbate post-calving
under-nutrition problems, priority in terms of feed allocation should be given to the
post-calving period. This can be achieved by shedding cows out from a moderate plane of
nutrition to a high plane as they calve, by strip grazing, shifting into saved feed at the start
of calving or calving onto spring growth. Some farmers, by calving late enough are able to
set stock cows amongst ewes and lambs at calving. Whatever system is used to apportion
feed, CS at calving is critical because it affects CS at mating, one of the most critical points
in cow management.
3.4.4
Calving to mating
Research suggests that Angus and Friesian cross beef cows need to eat in excess of 12 kg
DM /day from the day of calving through to mating.
Larger breeds will require
proportionately more. How this feed demand is met will depend on the time of calving, but
even herds calving close to their pasture growth curve will need some feed carried forward
from late winter. The area chosen for calving should be of easy contour and free of hazards
like creeks, tomos (underground holes) and swamps as these cause significant calf losses.
Post-calving nutrition is critical for several reasons:
•
Cow survival - the majority of cow deaths from hypomagnesaemia occur
post-calving and peak in the second week of lactation as the milk demands of the
calf increase. Provision of high quality pasture above 2500kg DM/ha (12 cm high)
is the key to its prevention. In some conditions, magnesium supplementation may
be required for a period during and after calving. Other metabolic conditions that
can occur at this time of the year are milk fever and ketosis. However they play a
very minor role in beef cow losses and are also prevented by correct cow condition
at calving and post-calving nutrition.
•
Calf growth rates - cows under-fed in early lactation will buffer their calves by
losing liveweight to maintain milk production. However, with high milk producing
Hereford x Friesian cows at a CS of 2.5 (5) or better at calving, it may be
necessary to restrict feed for the first 3-4 weeks post-calving. This is because the
calves are unable to consume all the milk produced by these high producing cows.
A recent trial indicates that a pasture sward height of 6 cm is sufficient for
beef x dairy heifers during the first month of lactation, increasing to 10-12 cm
during the second month of lactation.
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
34
Calves should gain at least 1.0kg/hd/day while suckling their dams. Milk makes up
a large proportion of their diet up to 12 weeks of age after which they can consume
up to 50% of total diet as grass.
•
Subsequent cow pregnancy rate and calving pattern – There are two aspects to
consider:
1. Whether the cow is pregnant or not
2. When the pregnancy was achieved
Cows fed in excess of 12kg DM/day from calving until prior to mating should be near a
condition score of 3 (6+) at mating. In this condition they will have high conception rates
(>95%) over a breeding interval of 63 days or 9 weeks assuming bulls are fertile.
Under-nutrition in the period from calving to mating can depress pregnancy rates. There
have been numerous trials to illustrate this, e.g. Table 3.5.
Table 3.5:
Effect of post-calving pasture allowance on cow pregnancy rate (Nicoll,
1979)
Post Calving
Nutrition
Allowance
kg DM/day/cow
Pregnancy
Rate
High
20
100%
Low
8
78%
This depression in pregnancy rate is produced as a result of lengthening of the post partum
anoestrus period and a reduction in conception rates. A cow has only 85 days to get
pregnant to calve on a 365 day schedule. Post-partum anoestrus periods longer than this,
and/or low conception rates leaving the cow empty at 85 days, will result in a later calving
next year. If these factors leave the cow empty after around 120 days then she will
generally be unable to get in calf because of bull withdrawal.
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
35
3.4.5
Mating - weaning
If a 63 day breeding interval is used for mature cows, then calves will be aged between
80 to 140 days at bull withdrawal. Weaning can be carried out at this stage but very high
quality feed is required to achieve calf liveweight gains of the same order as later-weaned
calves (e.g. at six months). Cows with a condition score of 3 (6) or better at mating can be
used in the late summer-autumn period to clean up low quality summer pasture with their
calves at foot. They will lose some body weight (20kg) while ensuring milk production is
maintained for their calves but if weight loss is too severe some minor effects in calf
weaning weights can result. Care is obviously required as calves are also competing at this
time for available pasture. Age at weaning obviously has an impact on calf weaning weight.
There are reasons for weaning both early and late, depending on weather and feed supplies
(Chapter 2).
3.5
Matching nutritional requirements to the seasonal pasture supply
pattern
The main management decision that affects the matching of the cow’s needs to pasture
production is the time of calving. Since most of New Zealand’s beef cows are run on farms
where sheep contribute the majority of stock numbers then the time of calving will also be
influenced by the needs of other stock classes, usually lambing ewes. As always, it is
important that the cow complements other livestock classes rather than competing with
them.
In Figure 3.1, a stylised cow feed requirement graph is shown with an example pasture
growth curve to demonstrate the effects of different calving dates on the match between
feed supply and animal demand. A mid October to late November calving span best suits in
this example.
Once timing of calving has been decided upon, there are advantages in managing the entire
herd to calve as quickly as possible during that period, rather than extending calving over
many months. Most farmers who farm beef cows restrict mating to 9 weeks or less. They
should aim to get as many of the cows pregnant as possible during the first 3 weeks of
mating to enable more controlled management. If all cows are at the same stage of
pregnancy/lactation feed budgeting will be easier.
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
36
Figure 3.1:
Matching beef cow nutritional requirements to Taihape hill country pasture
growth. The pasture growth curve is the average of 3 years of data.
Source: Hughes and Morris (1998).
3.6
Supplementary feeding of beef cows
The transfer of surplus pasture in spring/summer through to winter via the seasonal cycle of
body weight change in the mature beef cow is a key component to her successful
integration into hill country management systems. However, if supplements are to be used,
conserved pasture (hay, silage or autumn/winter annual feed) or nitrogen fertiliser are the
most common due to cost. In some cases winter crops may be grown (green feed oats) but
these are more likely to be used for growing cattle.
The main purpose for feeding
supplements in beef cow herds is to overcome winter or summer deficits. Supplements can
supply 20-80% feed intake during these seasons and in some cases may be the sole feed
in the cow’s diet. Supplementary feed does not need to be fed in some districts, such as
the Waikato or Northland, as pasture feed supplies can be matched with cow demand.
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
37
Silage is more nutritious and easier to make than hay but has the disadvantage of requiring
machinery for feeding out unless fed via a self-feeding system (see below). Silage can be
made under a wider range of weather conditions and has the big advantage that it is often
cheaper to make than hay, especially if stored as a stack. Hay can be a viable alternative
when equipment is not available and only small amounts are fed to animals. It can also be
easily transported and hence brought in to a hill country property with little flat land.
Some farmers use self feeding systems to feed silage. A common practice is to set up a
barrier or platform which could simply be an electric wire placed up against the silage stack
and moved forward each day. Cows can be maintained on 100% silage through to the last
2 to 3 weeks of pregnancy, or they can have a percentage of their diet as silage and have a
run back into an area of grass each day. Cows can easily eat 7-8 kg DM of silage per day.
It is difficult in most hill country environments to have enough stock to cope with the very
rapid rate of pasture growth in the late spring. The options of taking areas out of grazing for
hay, silage or winter crops are not appropriate for hill country. Beef cows are very useful to
"mop up" a proportion of this spring pasture growth flush. When pasture reaches a height of
8 cm or more, beef cattle are capable of eating much more than they need for their own
maintenance and milk production and can readily gain liveweight at 1.0 kg/day. In this way
cows play an important role in transferring feed from the late spring/summer to winter via
stored body fat.
The pasture required for 1.0 kg liveweight gain per day for 150 cows for 30 days is around
30 tonnes of dry matter. This is the equivalent of 1300 conventional hay bales. So the
statement that "the beef cow is a self-propelled hill country hay baler that uses no string" is
well founded. This surplus feed is stored as liveweight (mainly fat) at very little extra cost as
it takes relatively little extra energy to maintain a heavy fat cow than a light thin one.
Every 10 kg of extra liveweight that a beef cow takes into the autumn/winter represents a
saving of 8% of her feed requirements over the 100 day winter period. As she loses body
weight, she effectively feeds herself. In addition there are no non-biodegradable residues of
plastic bale covers left or fossil fuel used in feeding out.
If required, a wide variety of supplements are available and Appendix 1 lists the nutrient
composition of a variety of feeds that could be fed to cattle. Dry matter %, energy content
(MJ ME/kg DM), crude protein and mineral concentrations are given. Note the varying
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
38
energy content of good versus poor quality hay and silage. In many instances, it is not
economic to feed the supplements listed.
3.7
Assessing the adequacy of feeding
There are several methods by which to assess the success or otherwise of a feeding
regime. Weighing cattle and calculating average daily liveweight gains per head between
two weighing dates is the most obvious method used. There are problems sometimes in
interpreting the result as gut fill can result in an over estimate of liveweight by up to 7%.
This source of variation is minimised by weighing cattle at the same time of day at each
weighing and being careful about standardising weighing at either the start or end of the
grazing of a paddock. It is not necessary to weigh every animal and farmers will often weigh
an indicator mob to assess how feeding is going. Frequent weighing is onerous but does
mean a rapid response to any problems is possible. Alternatively, animals can be weighed
occasionally and their liveweights compared against target values.
Assessment of residual pasture mass will also give an indication of how livestock are
performing and is easier (especially if done by eye appraisal). If animals are grazing
pastures out to less than 1000/kg/ha then the chances are they will be growing at around
0.2–0.5 kg/day, whereas if they leave 2000 kg/ha they are likely to growing in excess of
1.0 kg/day. This depends on the season and on the pre-grazing herbage mass and quality
and is dealt with in more detail elsewhere. (See Further Reading at the end of this chapter).
In the beef cow herd there are some indictors that can point to longer term problems with
feeding. These include calving and weaning percentages, length of the calving period,
range in size and age of calves at weaning, and low in-calf rates. Low weaning
percentages, a long calving period and a wide range of calf sizes at weaning could all be
indicators of poor nutrition. Mating and calving dates are also an indication of the closeness
of the match of animal requirements with seasonal pasture growth.
The key times likely to influence production and profitability are calving, mating and
weaning. Assessment of cow liveweight at these times will provide information that is vital to
for feed planning. An accurate assessment of cow body reserves can be an important aid
towards optimising nutritional management and reproductive efficiency. Interpretation of
liveweights can be difficult owing to differences in mature size of cattle, stage of pregnancy,
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
39
and gut fill as described above. Hence, the introduction of a body condition scoring system
which allows cow body reserves to be assessed without the need for weighing.
3.8
Condition scoring
Condition scoring (CS) provides a measure of the level of body reserves of a cow
independent of liveweight, and is a more reliable description of cow condition than is
liveweight alone. It can be used as an aid when making management decisions. The
method involves assessing the level of fat cover on the rear half of the cow’s body
(see Appendix 1). Two systems are in use. The 0 to 5 scale works in increments of 0.5
(Table A1.1A), and is widely used in the Australian beef industry and the sheep industry in
New Zealand (Lowman and others, 1976). The 1 to 10 system is the same as that used in
the New Zealand dairy industry (Table A1.1B). Both systems have their merits and are both
effective. Cows can be scored for body condition regularly, particularly in cases where
weighing is not practical. The technique is easy to learn and does not require special
equipment. Two research studies indicate that one unit change in CS in British breeds of
cattle could be taken as equivalent to 50 kg (0-5 scale) liveweight. For Friesian, and large
European breeds (Charolais, Simmental) it may be equivalent to 100 kg (Lowman et al.
1976). On the 1 to 10 scale, one unit change is equivalent to 25 kg liveweight for smaller
breeds and 40 to 50 kg liveweight for bigger breeds.
There are five occasions when it may be beneficial to condition score beef cows. They are:
•
Weaning time - this ensures young cows (heifers) are given priority if they are in
poor condition
•
30-45 days after weaning - to see how feeding is going and adjust accordingly
•
60-90 days prior to calving - last opportunity to get things correct prior to calving
•
Calving - separate the thin cows and priority feed these
•
Mating - gives an indication of next year’s production levels
Target liveweights and CS for various sized beef cows at the critical times of year, are given
in Table 3.6 Note three different sized cows are given. These could represent different cow
breeds on the same farm (e.g. Angus, Hereford x Friesian, or Hereford x Simmental) on
different classes of country such as hard hill country where mature liveweights are poor
through to easy well developed country where mature liveweights are good.
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
40
Table 3.6:
Target seasonal liveweights and CS for various cow types
Cow size
*
Weaning
Mid Winter
Pre calving
Mating
Small
430
380
400
410
Medium
470
420
440
450
Large
550
500
520
530
Condition Score
(0 to 5 scale)
3 - 3.5
2.5*
2.5*
2.5 - 3.0
Condition score
(1 to 10 scale)
6+
5*
5*
5.5
These CS values are negotiable, provided the cow is fit and healthy, has good blood
magnesium levels and can gain weight to reach the mating CS targets shown.
In all instances in a well managed herd, cow liveweight is usually at its maximum in the
autumn at or just prior to weaning. Liveweight should be within 5% of maximum at mating.
Aim to manage breeding cows within the target ranges:
If breeding cows are too fat at calving (high CS), they are prone to get milk fever, can have
calving difficulties and may have reduced milk production. Most importantly, running beef
cows at too high a CS wastes valuable feed reserves.
Cows with a high CS at weaning can lose a lot of weight safely in autumn and winter, but
excessive weight loss in late pregnancy may increase the risk of pregnancy toxaemia
(ketosis) and grass tetany (staggers or hypo-magnesaemia). Returns to first oestrus will be
delayed if cows fail to reach the target CS shown for mating and they will suffer reduced
milk production and reduced calf growth rate.
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
41
3.9
Further reading
Geenty, K. G.; Rattray, P. V. 1987. The energy requirements of grazing sheep and cattle.
In: Livestock Feeding on Pastures. New Zealand Society of Animal Production.
Occasional Publication No 10: 39-54.
Hughes, P. L.; Morris, S. T. 1998. Management solutions for beef cows. New Zealand
Beef Council Southern Regional Field Day, Gore, 8 May 1998, Alexandra.
Nicoll, G.B. 1979. Influence of pre- and post- calving pasture allowance on hill country beef
cow and calf performance.
New Zealand Journal of Agriculture Research 22:
417 - 424.
Morris, S.T. 2007. Pastures and supplements in beef production systems. Ch 14, In:
Pasture and Supplements for grazing livestock. A book published by New Zealand
Society of Animal Production, c/o Dairy NZ, Hamilton, New Zealand. Occasional
Publication No. 14.
Nicol, A.M.; Brookes, I.M.
livestock.
2007.
The metabolisable energy requirements of grazing
Ch 10, In: Pasture and Supplements for grazing livestock.
A book
published by New Zealand Society of Animal Production, c/o Dairy NZ, Hamilton,
New Zealand. Occasional Publication No. 14.
Smeaton, D.C. 2007. Feed requirements of beef calves from age 6 months to slaughter,
Ch 5, In: Profitable beef production, A guide to beef production in New Zealand. A
book, published by Meat & Wool New Zealand, Beef Council, Third Edition.
Meat & Wool New Zealand, PO Box 121, Wellington.
Profitable Farming of Beef Cows
Chapter 3: Feeding beef cattle
42
Chapter 4: Reproduction in the beef cow herd
Summary
A major factor determining the productivity and profitability of beef cow herds is their
reproductive performance. The efficiency of a beef cow enterprise depends on the cow's
lifetime output (total liveweight of calves weaned/cow). Reproductive efficiency in cattle, as
measured by the number of calves born and weaned each year per 100 females in the
breeding herd, is considered the most important economic factor in cattle production.
Reproduction has at least twice the impact of growth or carcass characteristics on
profitability for cow-calf producers who sell their calves at weaning. A high lifetime output
for a beef breeding cow depends on a high reproductive rate where the target is as close as
possible to one calf per year per cow in the herd (100% calving).
Useful definitions of reproductive efficiency that can be measured in beef cow herds are:
•
Pregnancy rate - the number of cows pregnant per 100 cows joined with the bull.
•
Calving rate - the number of cows calving per 100 cows joined with the bull.
•
Calf survival - number of calves weaned per 100 calves born.
•
Calf weaning rate - number of calves weaned per 100 cows joined with the bull
Survey data indicate that the average calf weaning rate in New Zealand is static at 80 to
84%. This is in spite of the fact that considerable variation exists in calf marking %2 among
herds, from year to year in the same herd. We can conclude from this data that there is
considerable potential to improve reproductive efficiency in our beef cow herds but that it
has proven to be very difficult to achieve change.
Useful reproductive targets for an adult beef cow herd are:
2
•
A 12 month (365 day) mean calving interval
•
A 63 day (3 cycles) mating period for cows
•
A pregnancy rate of at least 95% for adult cows
•
A calf weaning rate of at least 90% in adult cows (some do better than this)
•
Less than 3% abortion rate
•
At least 60% of cows calving in the first 21 days of calving
Calf marking %, recorded in mid-lactation is a commonly used proxy for calf weaning %.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
43
•
Less than 5% incidence of calving difficulty (difficult birth)
It is usually more profitable to first calve heifers at 2 rather than 3 years of age because:
•
Lifetime output is increased by about 10%
•
Land use for heifer rearing is reduced by nearly 50%
•
Rate of genetic gain is increased (especially for bull breeding herds).
•
Information for selecting replacement heifers is available much earlier in a female’s
life - this is especially so if more heifers than are required as replacements are
mated
This chapter discusses all aspects of beef cow reproductive management including factors
affecting calving difficulty, bull performance, pregnancy detection and new reproductive
technologies including twinning and cloning.
4.1
Introduction
A major factor determining the productivity and profitability of beef cow herds is their
reproductive performance. The efficiency of a beef cow enterprise depends on the cow's
lifetime output (total liveweight of calves weaned/cow). This is a complex trait affected by
many factors (Figure 4.1).
A live calf born and weaned to each breeding female each year is the primary objective for
successful reproduction. However, cows are not managed as individuals but as a herd, so
the economic evaluation of total herd reproductive performance is critical. Reproductive
efficiency in cattle, as measured by the number of calves born and weaned each year per
100 females in the breeding herd, is considered the most important economic factor in cattle
production. Reproduction is at least twice as important as growth or carcass characteristics
for cow-calf producers who sell their calves at weaning.
A high lifetime output of a beef breeding cow depends on a high reproductive rate where the
target is as close as possible to one calf per year per cow in the herd. The production cost
of failing to rear a calf is high and is difficult to make up. For example a cow that rears
7 calves each weighing 220 kg has a total lifetime output of 1540 kg of calf weaned. To
produce the same total lifetime output in 5 calvings would require an annual calf weaning
weight of 308 kg.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
44
Useful definitions of reproductive efficiency that can be measured in beef cow herds are:
•
Pregnancy rate - the number of cows pregnant per 100 cows joined with the bull
•
Calving rate - the number of cows calving per 100 cows joined with the bull
•
Calf survival - number of calves weaned per 100 calves born
•
Calf weaning % (rate) - number of calves weaned per 100 cows joined with the bull
Each of these reproductive indices are useful in determining the reproductive efficiency of a
beef cow herd as they allow abortion rates, postnatal calf mortality rate and calf losses to
weaning to be calculated. These indices or ratios have the limitation that they take no
account of the duration of joining or the interval between calvings. Furthermore it takes no
account of the fact that some females with the potential to produce calves are not given the
opportunity (e.g. yearling heifers). The indicators also assume a natural mating system with
bulls (probably 98% of beef cows are mated in this manner), taking no account of age and
number of bulls used or the liveweight of cows in the herd all of which can contribute to
overall herd reproductive efficiency.
Figure 4.1:
The major factors influencing weight of calf weaned per cow bred.
Source: Taylor and Field (1999).
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
45
4.2
Potential reproductive rate
The reproductive rate of beef herds has been documented by the Meat & Wool New
Zealand Economic Service which records the number of calves marked per 100 cows joined
with the bull (calf marking percentage).
Note there are few calf deaths between calf
marking (when calves are around 60-90 days of age) and calf weaning. The survey data
indicate that the percentage of calves weaned is static at 80 to 84%. This is in spite of the
fact that considerable variation exists in calf marking percentage among herds and there is
often variation in pregnancy rate from year to year in the same herd. We can conclude from
this data that there is considerable potential to improve reproductive efficiency in our beef
cow herds but that it has proven to be very difficult to achieve change.
In New Zealand where pasture production is seasonal, most beef cow farmers have a
compact calving season, usually in spring. The biological timetable must be worked to a
tight schedule if a 365 day calving interval is to be maintained because:
•
Pregnancy (gestation length) is about 282 days (range 270 - 290).
•
To maintain a calving interval of one calendar year there are only 83 "non pregnant"
days available to the cow to get pregnant.
An excessive calving spread reflects reduced efficiency and reduces the likelihood of cows
getting pregnant.
The advantages of a compact calving include:
•
Easier allocation of feed and metabolic supplements to meet the cow’s feed
requirements
•
Easier allocation of calving paddocks
•
Ease of supervision at calving
•
An even line of weaners for sale
•
An even line of replacement heifers
•
A higher proportion of cows are likely to be cycling when the bull goes out
•
Heavier average weaning weights.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
46
It is relatively easy to place a monetary value on a condensed calving pattern compared to
a longer period. Consider two herds:
Herd A. – Assumptions; spread calving:
•
105 day calving period 15 August to 30 November
•
Equates to bulls out 1 November and in on 20 February (i.e. 5 cycles of mating)
•
Calving spread as in Figure 4.3
•
Calf birth weight of 35 kg
•
Weaning 1 March i.e. 200 days from start of calving
•
Average LWG birth to weaning = 1.0 kg/calf/day
•
Calves in each 21 day spread are taken on average to be born at the mid-point
•
Weaning weights calculated as:
(1st period average age = 190 days (mid way 180 - 200 days)
liveweight = (190 x 1.0) + birthweight (=35 kg) = 225 kg
Subsequent calf weights for each 21 day spread are:
1 – 21 = 225 kg
22 – 42 = 203 kg
43 – 63 = 183 kg
64 – 84 = 61 kg
85 – 105 = 140 kg
The average weaning weight for this cow herd is 187 kg.
Herd B. – Assumptions; condensed calving:
•
63 days calving period 15 August to 18 October
•
Bulls out 20 November and in 20 January (3 cycles)
•
Calving spread as in Figure 4.4.
The average calf weaning weight for Herd B would be 215 kg (using the same assumptions
as for Herd A).
The advantage of Herd B over Herd A is 28 kg. If we value calf liveweight at $2.20/kg, the
advantage to a calf from Herd B is $62 and for a 200 cow herd with a 90% weaning rate the
advantage is over $11,090.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
47
Figure 4.3:
Typical hill county calving spread (Herd A)
• This calving pattern coincides with
1 November - mid February mating
• Calving period: 8 August – 22 November
Figure 4.4 Preferred calving spread for hill country herd (Herd B)
• This calving pattern coincides with a
20 November - 20 January mating period
• Calving period: 29 August - 29 October
In practice there is often a compromise between acceptable duration and timing of calving,
and potential reproductive performance.
It is the successful management of this
compromise that is the key to successful reproduction in beef breeding cow herds.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
48
We can now, however, identify some useful reproductive targets for an adult beef cow herd.
•
12 month (365 day) mean calving interval
•
A 63 day (3 cycles) mating period for cows
•
A pregnancy rate of at least 95% for adult cows
•
A calf weaning percentage of at least 90% in adult cows (some do better than this)
•
Less than 3% abortion rate
•
At least 60% of cows calving in the first 21 days of calving
•
Less than 5% incidence of calving difficulty (difficult birth)
To the above list we can add targets for replacement heifers (these will be discussed in
more detail later).
•
Mate heifers for only 42-45 days (2 cycles) with a target 85% in calf rate
•
70% calve in first 21 days of mating
•
less than 10% incidence of calving difficulty
Note - An oestrous cycle is about 21 days and 2 cycles about 42 days. Some farmers also
mate cows for 2½ cycles i.e. 7½ weeks = 52 days to ensure a cow that cycles on day 22
which is not mated and cycles 22 or 23 days later has an equal chance of being mated
twice. If a 42 day mating was used this would not be the case and the cow would have only
one opportunity to be mated.
Another reason for restricting mating to 2½ to 3 cycles (53-63 days) is shown in Table 4.1.
In this example the herd that was mated for 105 days (5 cycles). The entire herd was
cycling when the bull was introduced, and a 60% conception rate was assumed (normal for
natural mating, usually ranges from 50% to 75%). After 63 days of mating 94% of cows
would be pregnant, but it would take another 42 days on average for the remaining cows to
get pregnant.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
49
Table 4.1:
Pattern of mating and conception during a 105 day mating period -
assuming a 60% conception rate (Morris 1998).
Days since start of
joining
Number on heat each
21 days
Number pregnant each
21 day period
21
100
60
42
40
24
63
16
10
84
6
4
105
2
2
0-105
164
100
4.3
Reproductive management of beef cattle
4.3.1
Management and age at first calving of heifers
A recent Meat & Wool New Zealand survey (Heuer, 2007) suggests about 55% of beef
heifers are first mated at 15 months of age. It is usually more profitable to calve heifers first
at two years of age than 3 years.
The main reasons for this are because:
•
Lifetime output is increased by about 10% (an extra 0.7 calves or 150kg of calf
weaned)
•
Land use for heifer rearing is reduced by nearly 50%
•
Information for selecting replacements is available much earlier in a female’s life.
This information is particularly useful if more heifers are mated than are required as
replacements
•
Increased rate of genetic gain (especially for bull breeding herds).
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
50
The main reasons for farmers failing to adopt the practice of 2 year-old calving in
New Zealand beef cow herds are:
•
Poor performance at the next mating (often one of the costs of 2 year-old calving is
a 5-10% lower pregnancy rate in the next breeding period)
•
Fear of increased incidence of calving difficulty (dystocia) and associated increase
in calf mortality and possibly heifer mortality
•
A failure to achieve target liveweights during rearing and at mating, thereby
jeopardising subsequent reproduction performance
•
Concern that the heifer’s mature size and productivity will be reduced.
•
Stage of farm development - on harder hill country or less developed country (in
terms of pasture production and quality), heifers may fail to reach the required
mating liveweights
•
Reduced management flexibility (pregnant heifers require extra feed and there is an
extra mob to manage)
•
Overall increased management skills are required
While the evidence consistently favours mating heifers at 15 months of age to increase
production and profit per animal or per herd, the evidence is less convincing when
accounting for feed costs required to achieve this increase.
A New Zealand study (Table 4.2) found that mating heifers first as yearlings as opposed to
two years of age resulted in efficiency increases (expressed as kg of calf weaned per kg of
cow wintered) of 2% for Angus dams and 6% for Hereford x Friesian dams (H x F). For
both dam breeds, 7% fewer cows were run per hectare when mating heifers first at
15 months of age, reflecting higher winter liveweight gains and feed requirements of mated
yearling heifers.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
51
Table 4.2:
Effects of age at first mating and cow breed on numbers of cows and
replacements wintered, winter feed requirements and calf production when considered at
the same winter feed requirement (adapted from McMillan and McCall 1991).
Angus
2 year old
Number wintered
(MA cows plus replacement heifers)
yearling
2 year old
yearling
100
93
89
83
Feed requirements
(kg DM/animal/day)
4.4
4.7
4.9
5.2
Females joined
70
74
61
66
No. calves born*
70
75
61
68
161
165
190
194
100.0
101.7
108.2
114.8
Average calf weaning weight (kg)
Efficiency ratio
(total kg of calf weaning wt)
*
Hereford X Friesian
Number of calves weaned per number of females wintered (including replacement heifers)
Higher efficiency of H x F dams compared with Angus dams for yearling compared with
2 year mating was due the to lower relative performance of Angus heifers compared with
mixed age cows. Angus dams weaned 58% calves per heifer joined as yearlings and 83%
calves weaned per cow joined for mixed age cows whilst H x F dams weaned 75% and 85%
respectively. Using these parameters, a higher proportion of non-pregnant Angus than
H x F heifers would be wintered. From this study, the authors suggested that benefits of
changing from 2 year to yearling mating would be minimal unless accompanied by a switch
to more productive breeds. In a follow-up study McMillan and others (1992), found an 8%
increase in herd efficiency (weight of calf weaned per unit of winter feed required) was
obtained when Angus heifers were mated first as yearlings as opposed to 2 years of age.
The increase in efficiency for this herd under yearling mating was comparable to the H x F
in the previous study.
A prerequisite to mating heifers at 15 months to calve at 2 years of age is that the heifer has
attained puberty. Puberty in the heifer is marked by the start of regular oestrous activity,
associated with ovulation. All heifers should reach puberty well before the planned start of
mating, so each has exhibited at least one "heat" before the start of mating. This will ensure
there is a high probability that all will be mated and conceive during the first 6 weeks of
mating.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
52
4.3.1.1
Critical minimum weight
Heifers mated as yearlings have a requirement for high quality feed if they are to reach a
critical minimum weight (defined as the weight at which 85% or more heifers get pregnant in
a 42 day mating period) and rebreed successful. Under harder hill country this condition
might not be met. Target live weights for mating British breed heifers at yearling age are
shown in Table 4.3. From New Zealand breed comparisons, Continental x British breed
heifers were on average 30 days older and 30 kg heavier at puberty than straightbred
British breed heifers, suggesting higher target live weights for these later maturing breeds.
4.3.1.2
Checklist for successfully mating heifers at 15 months
• Set a growth pathway from weaning to a minimum joining live weight at 15 months
(Table 4.3). An appropriate minimum target might be 270 kg for Angus and 300 kg
for later maturing breeds
•
Mate heifers for 42 days – aim for a target pregnancy rate of 85%
•
Mate heifers at the same time as older cows as earlier mating can result in below
target pregnancy rates at the next mating due to delayed returns to oestrus (see
later)
•
Mate more heifers than are required as replacements and cull empty heifers
following pregnancy testing. Non pregnant at yearling breeding is highly repeatable
•
Cull late calvers to ensure that 70% calve in the first 21 days
•
Understand the concept of Expected Breeding Values (EBVs) and select service
sires from easy calving breeds/herds and with a high direct calving ease EBV. If
these EBVs are not available select sires with below breed average birth weight
EBVs, below breed average gestation length EBVs but with above breed average
200 or 400 day weight EBVs (‘curve bender bulls’)
•
Use sires from the same or smaller breeds.
•
Provide assistance at calving where necessary
•
Run as separate group until second calving
•
Strive for 90% calf survival to weaning
•
At least 90% of heifers should be pregnant again as R-3 year olds
There are additional feed costs, when mating yearling heifers. If yearling heifer in-calf rates
are less than 70% there may be no benefits compared with calving first at 3 years. Every
farm needs to be evaluated separately to ensure benefits are realised.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
53
Table 4.3:
Target live weights for mating Angus or Friesian x Hereford/Angus cross
heifers first at 15 months of age
Age (months)
Weight (kg)
Weaning
6
200-220
st
10
220-240
st
1 mating
15
270-300
2nd winter
22
400-450
Pre-calving
24
440-480
27
420-450
1 winter
nd
2 mating
4.3.2
Time and duration of calving
It is important to distinguish between mating date (the day the cow is mated) and joining
date (the day the bull is put in with the cows). There are risks associated with too early a
mating date and likewise too late a mating date.
Risks associated with too early a mating date are:
•
Cows calve before spring flush
•
There is greater requirement for saved (winter) pasture pre-calving
•
Cows are usually in a lower condition score at joining
•
Cows exhibit longer post-partum anoestrus intervals
•
Cows often calve later in the following year
Risks associated with too late a calving:
•
Waste of (surplus) spring pasture
•
Smaller calves at weaning
•
Peak lactation is reached too late in the summer-dry risk period
•
Reduced opportunities for re-mating
•
Reduced lifetime calf output
Generally (except for South Island high country) beef cows are typically planned to calve at
the same time as, or before lambing. Many farmers are now questioning this as being too
early and in terms of profitable use of winter feed and efficient reproduction this is certainly
the case. Time of mating for heifers is important and if they are mated too early in spring
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
54
they will have less time to reach puberty and the required "critical minimum mating weight".
In reality, most beef cows are run with sheep and the optimum time to mate depends on
individual property features as described in Table 4.4.
Table 4.4:
Factors indicating later calving would be recommended.
Factor
Trend in factor
Recommendation
Cattle : sheep ratio
High ratio
Later calving
Stocking rate
High
Later calving
Cow genotype
More productive
Later calving
Cow management
Cows consume spring surplus pasture and
are used to maintain pasture quality
Later calving
Calving pattern is an excellent guide to the suitability of mating date. If less than 50% are
calving in the first 21 days of calving then mating date is probably too early. The target is
60% of cows and heifers mated in first 21 days of mating – so that at least 60% should
calve in the first 21 days of calving.
It is a relatively simple procedure to collect this
information. Simply count the number of calves born per week and then plot them over
21 day periods throughout the calving period. This will give a detailed picture of how the
previous year’s mating went.
4.3.3
Age of cow and reproductive performance
Young cows often have a lower average reproductive performance than older cows,
although the extent of the difference can depend on breed type. Pregnancy rate increases
up to at least 6 years of age, then remains stable until about 9 or 10 years of age, after
which it starts to decline.
The most comprehensive New Zealand study on age of cow and reproductive performance
(7500 matings) is summarised in Table 4.5. Results suggest that beef cows in a mixed age
herd should not be culled on age until they are over 10 years.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
55
Table 4.5:
Effects of cow age at mating on pregnancy rate, ease of calving and calf
weaning %. Source: Morris (1998).
Age at mating
No. of
records
% cows
pregnant
% calved without difficulty
% calves weaned
per female/mated
2711
2022
1803
1639
77
74
82
89
84
92
95
96
63
63
74
83
15 months
27 months
3 years
4 years
4.3.4
Calving difficulty (dystocia)
Calving difficulty or dystocia has a major effect on the subsequent production and
reproductive performance of the affected cow. The incidence of calving difficulty varies and
is probably responsible for up to two thirds of calf deaths in beef cow herds (average calf
mortality in herds is 0 - 15%). The incidence can be much higher in first calving heifers and
can be quite low <2% in adult cows. When mating heifers at 15 months to calf first at
2 years of age, managing for a low incidence of calving difficulty is important.
Factors that influence the incidence of calving difficulty:
•
Calf size - calf birth weight is the most important factor affecting calving difficulty.
Most of the other factors influencing calving difficulty levels are mediated through
calf birth weight so that controlling calf birth weight will eliminate calving difficulty
from the herd.
•
Breed of sire of calf - some breeds especially.
Continental breeds have high
incidences of calving difficulty (see Table 4.6). Jersey sires have low to negligible
calving difficulty.
•
Sire within breed - selecting the correct bull will also reduce calving difficulty.
Choose bulls with below average estimated breeding value (EBV) for birth weight.
•
Sex of calf - male calves are about 1-2 kg heavier than female calves and tend to
have a 1-2 day longer gestation than heifers (see Table 4.6).
•
Plane of nutrition - excessive growth or liveweight gain in late pregnancy can affect
the size of the calf and the amount of fat laid down in the pelvis region. This is
important in heifers, since their birth canal is small - but remember heifers need to
be well grown to have developed a sufficiently large birth canal to be able to deliver
a calf. Feeding levels have to be extreme to manipulate birth weight as a heifer
buffers against low nutrition feeding levels by mobilising her energy to keep the
nutrient supply to calf.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
56
•
Breed of dam - the British beef breeds (Angus and Hereford) tend to have less
incidence of calving difficulty than dairy or continental beef crosses.
•
Gestation length - an extended gestation length will increase birth weight.
•
Season of birth - late season calvers tend to have higher birth weights than animals
that calve in late winter early spring.
Table 4.6 gives some comparative data on birth weight, gestation length, incidence of
calving difficulty and calf mortality from the only comprehensive breed evaluation carried out
in New Zealand. Note the relationship between birth weight, gestation length and incidence
of calving difficulty and calf death. One of the reasons that calving difficulty is high when
European continental breeds are used is the increased gestation length of calves sired by
those bulls.
Figure 4.5:
Changes in birth weight EBV through time in US beef breeds
Source: Kuehn and others (2008).
The most practical way to control or minimise calving difficulty is via bull breed and birth
weight EBV. It is also crucial that EBV accuracy is taken into account. Figure 4.5 shows
the results of efforts by U.S. breed societies to control birth weight EBVs. The results show
that progress can be made in controlling birth weight while still maintaining progress in say
yearling weight (not shown here). These effects will filter down to New Zealand through the
importation of genetics from Australia and the US by New Zealand beef breeders. Many
New Zealand breeders also apply similar selection processes to their breeding
programmes.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
57
Table 4.6:
The effects of breed of sire (averages of mating to both Angus and Hereford
dams) sex of calf and age of dam on calf birthweight, gestation length, incidence of dystocia
and calf deaths. (NZ data: Baker and others 1990).
Birthweight
(kg)
Gestation
(days)
% Calving
difficulty
% Calf deaths
to 48 days age
Jersey
27.4
283
0.9
1.8
Angus
29.6
281
3.6
4.1
Hereford
31.6
282
2.3
3.6
Friesian
31.9
280
4.6
2.9
Limousin
32.7
287
5.5
3.8
Blond d'Aquitaine
33.8
288
10.4
4.8
- German
33.5
285
7.3
5.2
- Austrian
34.4
286
9.6
10.5
- French
35.0
287
10.9
4.7
- Swiss
35.0
286
10.8
6.4
South Devon
34.4
286
7.1
5.0
Charolais
35.7
285
17.7
11.2
Chianina
36.8
288
15.1
6.1
Maine Anjou
35.7
285
13.7
8.4
Male
34.5
286
12.1
7.4
Female
32.3
284
5.0
3.9
Sire
Simmental:
Sex of calf
Age of cow at calving (years)
3
32.0
285
13.8
8.6
4
33.5
284
6.8
4.5
Older than 4
34.7
285
5.0
3.8
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
58
4.3.5
Post-partum anoestrus interval
The post-partum anoestrous interval (PPAI) is the time between calving and the first oestrus
after calving. Post-partum intervals are of prime importance in cattle where gestation takes
up to 282, days thereby leaving only 83 days to re-commence oestrous cycles and to
establish pregnancy if calving date is to be maintained.
The duration of the post-partum interval in beef cows is determined by:
1. Date of calving: Cows which calve earlier in the late winter/spring calving season
tend to take longer to experience their first post-calving oestrus than cows that calve
later in the calving season (Figure 4.6)
Heifers can take about 7 days longer to
cycle for every 10 days earlier calving.
2. Age of cow: In one study for example, PPAI for 2 year old cows was 90 days vs.
63 days for older cows. The practical significance of this effect is that the benefits of
mating heifers 3 weeks ahead of the mixed aged cow herd are often negated by
their longer PPAI. Research indicates that the range in PPAI is as shown:
a. 2 year old heifers 72 to 111 days
b. mixed aged cows 57 to 71 days
3. Breed of cow: In another study, Friesian cross heifers had an average PPAI of
90 days vs. 81 days for Angus heifers. This breed difference is likely to be related
to increased milk production and lighter condition (nutritional stress) in beef x dairy
animals.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
59
Figure 4.6:
The effect of calving date in spring calving cows on post-partum oestrus
interval (PPAI).
Table 4.8 provides an example of the relationships between calving date and feeding level
during the post-partum period.
A high level of feeding after calving does not fully
compensate for an early calving date. In contrast a medium-nutrition regime is adequate for
later calving cows. Photoperiod has some influence on PPAI with increasing day length
tending to reduce PPAI.
However, this is difficult to quantify in its own right because
increasing day length is closely linked to increasing pasture growth rates.
Table 4.8:
The effect of calving date and post-calving nutrition levels on PPAI (days)
Early calving
Late calving
July 21 – Sept 15
Sept 9 – Oct 10
High nutrition
67
57
Medium nutrition
83
62
Calving Period
Season of birth can determine PPAI. In spring-calving herds the interval ranges from 65-90
days while for autumn calving herds it is 31-51 days.
Cow condition, liveweight and liveweight gain post-calving are major determinants of the
post-calving interval in beef cows. In one trial an extra 20 kg post-calving liveweight was
associated with a 7 day shorter interval in heifers, compared with only 2 days in adult cows.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
60
4.3.6
Bull management
Most New Zealand beef cows are mated using natural mating with artificial insemination
being confined mainly to the bull breeding industry. Factors that contribute to the outcome
of natural mating include bull age, bull soundness and fertility, breed of bull and bull to cow
ratio.
•
Age:
Puberty is dependant on nutrition, age, breed.
This occurs in males for
New Zealand breeds at around one year of age (older in some continental breeds).
Yearling bulls make satisfactory herd sires if they are adequately grown (>350kg)
and run with no more than 25-30 cows each. Scrotal circumference is a good
indicator of puberty and bulls with a scrotal circumference less than 30 cm should
not be used.
•
Bull-to-cow ratio: Little New Zealand data exist as to the effects of bull to cow ratio
on herd pregnancy rate. It is normal practice for one bull to be joined with to 30-50
cows. If farmers wish to use fewer bulls of higher genetic merit, a higher ratio can
be used provided the bull is physically fit enough.
•
Soundness and fertility: Mating cow herds on undulating to steep hill country poses
extra problems for bulls. They must be able to seek out, find and mate oestrus
cows on broken terrain. Unstable footing during mounting can potentially lead to
damage to limbs, joints and genitals.
Every bull used needs to have a yearly
breeding soundness evaluation 30-60 days before the start of the breeding season.
Currently attempts are being made by the beef cattle stud industry in consultation
with the Sheep and Beef Society of the New Zealand Veterinary Association to
standardise a presale or pre-season bull soundness examination which could
include the items shown below:
•
Inspection for structural and inheritable faults
•
Examination/palpation of reproductive organs
•
Temperament, locomotory system assessment
•
Serving ability test
•
Diagnostic tests for BVD, EBL, Camplyobacter, Trichomonas
•
Semen evaluation (gross and morphology)
The degree to which these tests are used in the industry will depend on the level of risk
associated with using unsound bulls and animal welfare issues associated with some of the
testing procedures. There is little hard information on fail rates for the tests. If tests are
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
61
carried out for the first time in several years, anectdotal evidence suggests at least 25% of a
bull team could fail but with much lower fail rates in subsequent years.
There is variation in the assessment of the true level of risk associated with the prevalence
of semen faults in young bulls. Tattersfield and others (2006) found 0.6% of 175 sale bulls
surveyed were unsound on semen morphology with a further 10.5% temporarily unsound
and requiring repeat semen testing. They also found 21% of mixed age bulls failed this test
versus 5% of 2-year old bulls. There is variation within populations of bulls. Younger bulls
tend to have fewer semen quality issues than older bulls.
It is impossible to state
categorically that a bull is fertile but it is possible to minimise the risk. Semen testing is not
common in commercial herds. Clearly, where mixed age bulls are to be single sire mated
there are advantages of including semen evaluation in an attempt to mitigate risk.
As a bull ages, the risk of failure, for the service test in particular, also increases.
Procedures for assessing the mating potential of bulls have also been developed in
Australia.
The "serving capacity test" provides an indication of the ability of a bull to
successfully mate a given number of cows over a 3 week period. Serving capacity testing is
not recommended by Meat & Wool New Zealand for welfare reasons; a modified form called
serving capability testing has been developed by the New Zealand Veterinary profession.
This test simply determines if the bull is capable of mating an oestrus cow and does not
rank bulls. It is a less stressful test and is valuable in detecting arthritis and joint problems
with older bulls.
In practice, most bulls are used in syndicate matings (i.e. more than one bull per mating
mob) with 2 to 3 bulls per 100 cows. While this is an acceptable practice it uses a higher
proportion of bulls than is needed to achieve a high pregnancy rate. The extra bulls are an
insurance policy against any one bull failing during the mating period.
Bulls need to be in good condition (CS 3.5 (6 to 7)) but not over-fat prior to the mating
season. Check bulls at least twice a week during mating to observe them walking and to
check for anything unusual. If possible, watch bulls actually mating. It is a good idea to
have a spare bull available to replace any bull that breaks down over the mating period.
Some farmers rotate bulls after one cycle (or even 1 week) of mating. This is especially
important in single sire mated groups and acts as insurance against bull infertility.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
62
When a new bull is purchased remember it needs time to adjust to its new surroundings.
The bull should be run with a steer or old cow once it arrives at its new home, never run
with older bulls. Sometimes bulls purchased have not cut their second teeth - so feed
should be plentiful as this is a stressful time and they can loose condition.
4.3.7
Pregnancy diagnosis
Determining pregnancy in cattle is an important management tool.
The advantages of
knowing the pregnancy status of a beef cow herd are:
•
Allocation of feed
•
Saving feed by culling non-pregnant animals before the winter
An experienced veterinarian can determine the age of the foetus if pregnancy diagnosis is
done at the right time (8-12 weeks pregnant). This allows for prediction of calving dates and
more precise allocation of feed in late pregnancy and early lactation. It can also assist in
more efficient use of labour during calving especially if calves are tagged and weighed at
birth
4.3.7.1
Two methods of pregnancy diagnosis
1. Palpation of the uterus and its contents: this involves inserting a gloved and
lubricated arm into the rectum and feeling the reproductive tract. This was the
most common method used in New Zealand and is performed 6 weeks (for
heifers) and 8 weeks (for cows) after the bull is removed from the herd.
2. Ultrasonic detection of the foetus and its membranes using a portable scanner is
now the most common technique for determining pregnancy in cattle. Scanning
is faster and less demanding physically than rectal palpation and is becoming
the preferred technique. Scanning is done with a rectal probe. The technique is
often performed between 6 to 8 weeks after mating and allows for manual
checking of cows where either a foetus or an empty uterus cannot be visualised.
Pregnancies can be detected as early as 35 days. However accuracy and speed
of detection increases as pregnancies develop. At the other extreme, the later
that testing is left after bull removal, the more manual checking may be required
as pregnancies drop down over the pelvic rim beyond the reach of the probe.
Foetal ageing can also be performed but requires training and practice. The
most practical time for foetal ageing is when pregnancies are between 6 to 12
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
63
weeks of age. Depending on the length of the mating season, pregnancies can
be split into mating cycles, allowing for better feed allocation pre-calving.
Scanning needs to occur 6 to 8 weeks after bull removal. A complicating factor
is cows often are not weaned at this time requiring drafting of calves. Less
desirably, they can run up the race with the cows as they are usually large
enough by then to handle this.
Foetal sexing is possible using ultrasound but is technical and specialised. It is
best performed at 60 to 80 days of conception and requires a high resolution
scanner.
Sequential testing may be required due to foetal orientation and
accurate mating records are necessary.
It is more time consuming and
laborious and requires more experience.
Under good conditions with a long race holding up to 10 cows and when
pregnant/non pregnant diagnosis only is required, up to 200 cows an hour can
be scanned. As the dry rate increases this slows down the speed of operation.
Foetal aging also reduces speed to 80 to 100 cows an hour. However speed of
scanning is very variable under field conditions as many factors can influence
operator speed e.g. light, cow temperament, faecal composition, stage of
pregnancy, race length, race width, cat walk height, number of staff present. In
long races it is preferable to work from front to back to avoid having cows
stacking on top of each other. A dividing gate half way along can help alleviate
this problem as does race width (650 to 700 mm is optimum). Right handed
operators prefer the cat walk on the right hand side of the race when looking
forward. The top rail should not be too high above the cows, usually level or 200
mm above the cow’s back. The most common height for cat walks is 600 mm
with the top rail 900 mm to 1 meter above this. A generous cat walk width of
750 mm to 1 meter allows for operator safety and so people can pass each
other comfortably.
4.4
New reproductive technologies for use in beef breeding cows
A reproductive technology can be defined as any technology that impacts on the
reproductive performance of breeding cow or a herd of breeding cows. This definition
includes technologies which impact on the number of calves produced as well as the weight
of the calves at weaning time. Reproductive technologies can impact on cows or herds in a
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
64
variety of ways. They can improve calf productivity (number and weight of calves weaned),
herd management and genetic gain. Risks, costs and the level of technical input vary for
the options available. Most, if not all, of these technologies have direct application in the
dairy herd and this is where most reproduction technologies were first developed and
established.
Low technology options are mainly management options and tend to be low cost, low risk
and generate low to medium returns. These include the already discussed yearling heifer
mating system, highly productive breeding cows e.g. dairy x beef bred cows (Hereford x
Friesian), adjustments to the date of calving, pregnancy diagnosis and foetal calf ageing.
Medium technologies have a need for high technological input and are more costly. The
relevant technologies here are oestrus synchronisation, multiple suckling using an
additional foster calf, or the use of artificial insemination.
High technology options are costly and require a high level of technological input. They
include induction of twin pregnancies using embryo transfer, changing the sex ratio of
calves, and cloning.
Some technologies are discussed in more detail below.
4.4.1
Oestrus synchronisation
This is often a prerequisite to the use of AI and embryo transfer. In addition it may be used
to facilitate appropriate feeding and calving management since cows will all be at the same
stage of pregnancy. McMillan (1994) found that synchronisation of oestrus changed the
calving distribution with an earlier median calving date by about 10 days in synchronised
heifers. The effect of this earlier calving date was an improvement in calf weaning weight of
12 kg. Synchronisation costs are likely to be around $15 per cow and the 12 kg extra calf
weight covers these extra costs at a weaner price of $1.25/kg liveweight.
4.4.2
Artificial insemination (AI)
This can be used to obtain access to bulls which would otherwise not be available (e.g.
bulls from overseas).
AI is used to improve rates of genetic gain, or to limit sexually
transmitted diseases. The use of AI in beef cows in New Zealand is mainly limited to bull
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
65
breeding herds and is likely to remain that way in the near future. The intensive labour input
required for the identification, isolation and handling of cows on heat is not available in most
commercial extensively run beef cow herds. It is also difficult to maintain an adequate feed
supply for cows and calves close to cattle yards for the duration of the AI programme.
Another potential problem that limits the increased use of AI in beef cow herds is lack of
suitable progeny tested bulls. Unlike the dairy industry, where there are industry wide
progeny test schemes run by artificial breeding companies, there are no such schemes in
the beef industry and it is up to individual breeders or groups of breeders to progeny test
sires, using for example the BREEDPLAN scheme (Chapter 6).
4.4.3
Producing twin pregnancies
In cattle the natural twinning rate is 1% although Simmental herds may have up to 2.1%
twinning rate. Twinning can be induced by embryo transfer using either two transferred
embryos, or one transferred embryo to supplement the natural one produced by the cow.
Up to 101 calves may be born from one round of transfer (range is 10–101, with the
average 50-60). A second round of inducing twinning in cows which return to oestrus after
the first round can produce another 20-30 calves. Researchers are also working on a
vaccine to produce twinning in cattle. Selection is also possible but slow. Geneticists at
Clay Centre, USA have bred a herd of twin calving cows who have a twin pregnancy rate of
over 50% (Cummins and others, 2008).
Any of the above methods should ultimately be
able to achieve over 150 calves born per 100 cows.
Even if twin pregnancies have been achieved, twinning in cattle is not straightforward. Calf
losses at twin calving can be as high as 40%, mostly due to foetal malpresentation in the
birth canal (causing calves to be born dead) and mis-mothering and poor colostrum feeding
immediately after calving; often exacerbated, ironically, by high levels of human intervention
at calving. Even so, a high level of supervision at calving is required to ensure high twin calf
survival. If the twin calves survive and are bonded to the cow and feed well, there should
be few problems subsequently.
Twins will wean at a weight that is over 60% of cow
liveweight.
For productivity reasons, some managers foster a second calf onto a single calving cow.
This process is labour intensive immediately after calving and requires carefully followed
protocols to avoid calf illness. Financially, twinning by fostering, or using multiple suckling
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
66
nurse cows can be very profitable, even after allowing for the extra labour required at
fostering-on time. However, the practice has had only limited adoption in New Zealand.
Three technical barriers have to be overcome at an acceptable price for twinning in beef
herds to be a successful and profitable system:
•
Cows routinely become pregnant with twins
•
Cows deliver a high percentage of live twin calves at calving
•
Twin calves have high survival and are illness-free in their first month of life.
If the above obstacles were overcome, beef cow productivity and profitability would be well
placed to show similar gains to those achieved by the New Zealand sheep industry in the
last three decades.
4.4.4
Changing average calf sex ratio
Changing the average calf sex ratio could influence the economics and genetics of livestock
production in New Zealand. For example, a beef farmer could breed 80 steers and 20
replacement heifers from the 100 cows, thus increasing the value of their weaners (steers
or bulls are more valuable than heifers). However, the heavier birth weights of males can
lead to increased mortality rates from calving difficulty, especially in calving heifers, so this
would need to be allowed for. The technique is available commercially in New Zealand but
its adoption rate is still low due to technical difficulties and cost.
Sperm sexing occurs where the populations of x (female) and y (male) chromosome
bearing sperm in a semen sample are separated. At present they can be separated with
about 90% accuracy, using a fluorescent dye where the x chromosome absorbs more of the
dye than the y chromosome. The dyed sperm are then passed through a laser beam in a
sorter one by one. This gives them a charge, either positive or negative and they then pass
through an "electric gate" which sorts them into x and y groups based on their electric
charge. This method is relatively slow sorting only 100 sperm per second (Note that one
insemination dose for a cow, using frozen semen, requires 10 million sperm).
Sexed sperm is more likely to be used in laboratory based in vitro fertilisation (IVF) and
embryo production (IVP) to generate sex selected calves. This is a technology that will
probably be first used in the dairy industry where female calves are produced at initial
matings and the males at later matings.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
67
4.4.5
Cloning
Nuclear transfer (NT) cloning is an assisted reproductive technology which creates an
animal that is a genetic copy of the donor cell genome used in the procedure. Simply, it
involves microsurgery under the microscope to introduce the nucleus of a donor cell into the
cytoplasm of a mature cow’s egg that has had its own nuclear DNA removed. This
reconstructed 1-cell embryo is then artificially activated to commence development and is
grown in the laboratory for 7 days until it reaches the blastocyst stage (around 120 cells)
and can be transferred to the uterus of a recipient cow. Nuclear transfer technology has the
potential to replicate cloned animals from outstanding embryonic or adult genotypes,
including resurrecting animals for breeding after post-slaughter carcass assessment.
Cloning would be an attractive alternative to artificial insemination, which is not widely
adopted on extensive beef farms.
Although improvements have been made, the NT process remains inefficient. Presently, in
cattle, about 10% of NT embryos transferred to recipient cows result in viable calves. High
pregnancy losses throughout gestation and after calving reduce the acceptability of this
technology. Continued research aims to understand how it is biologically possible to take a
specialised cell from the body of a donor animal and generate a normal cloned animal.
Importantly, the sexually reproduced offspring derived from cloned parents appear normal.
This provides confidence for the main potential application of NT in agriculture; that is, the
production of cloned sires from genetically elite males for natural mating, to effectively
disseminate genetic gain. Nonetheless, the integration of cloning into beef farming systems
remains a future prospect dependent upon overcoming existing technical and biological
barriers, in addition to gaining widespread international regulatory and consumer
acceptance.
4.4.6
DNA parenting
Technologies using DNA parenting are used, albeit sparingly.
Some breed societies
require mandatory DNA parentage verification for breed registration purposes.
(It is a
requirement for all 2008 born Angus calves if they are to achieve breed registration). In
future this DNA testing could be extended to allow whole genome scans or single gene
tests to be run.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
68
4.5
Further reading
Anon. 2002. Bull Selection. A Beef Council Bull Publication. Available from Meat & Wool
New Zealand, PO Box 121, Wellington, New Zealand
Baker, R.L.; Carter, A.H.; Morris, C.A.; Johnson, D.L. 1990. Evaluation of eleven cattle
breeds for crossbred beef production; performance of progeny up to 13 months of
age. Animal Production, 50: 63-77.
Cummins, L.J.; Morris, C.A.; Kirkpatrick, B.W.
commercial production.
2008.
Developing twinning cattle for
Australian Journal of Experimental Agriculture, 48:
930-934.
Heuer, C. 2007. Management of beef cattle for high fertility. Part 4: Association between
farm management practices and beef cow fertility. Final Report to Meat & Wool
New Zealand, PO Box 121, Wellington, New Zealand.
Hughes, P. 2007. Evaluation of Bulls for Breeding Soundness: The Society of Sheep and
Beef Cattle Veterinarians NZVA Newsletter 32: 43-44.
Kuehn, L.; van Vleck, D.; Thallman, M.; Cundiff, L. 2008. Across-breed tables for 2008 with
year
2006
Angus
base.
Slides
presented
at
the
BIF
Conference.
http://www.bifconference.com/bif2008/ppt/LarryKuehn_GP.pdf.
McMillan, W.H. 1994. Current and emerging reproductive technologies for beef breeding
cows.
Proceedings of the New Zealand Society for Animal Production 54:
345 - 350.
McMillan, W.H.; McCall, D.G. 1991. Are yearling heifers mated and more productive cow
breeds worthwhile use of winter feed? Proceedings of the New Zealand Society of
Animal Production, 51: 265-269.
McMillan, W.H.; Morris, C.A.; McCall, D.G. 1992. Modelling herd efficiency in liveweight
selected and Angus control cattle. Proceedings of the New Zealand Society of
Animal Production, 52: 345-350.
Morris, C.A.
1998.
Reproductive management of beef cattle.
Management of Grazing ruminants in New Zealand.
In Reproductive
Ed. E.D. Fielden and
J.F. Smith. Occasional Publication 12: 145-156. Published by the New Zealand
Society of Animal Production.
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
69
Morris, C.A.; Packard, P.M. 1985. Progress with Beefplan. In, 1984-85 Annual Report of
the Ruakura Animal Research Station (Genetics Section), Ministry of Agriculture &
Fisheries, Hamilton, New Zealand, pp.76-77.
Parkinson, T.J.; Bruere, A.N. 2007. Evaluation of Bulls for Breeding Soundness 1st Edition
Publication No. 262 Published by VetLearn, Massey University, Palmerston North.
ISBN 978-09583634-2-0.
Smeaton, D.C.
2000.
Management and profitability of multiple pregnant/suckling beef
cows. A producer’s guide. A booklet available from Meat & Wool New Zealand,
PO Box 121, Wellington, New Zealand.
Taylor, R.E.; Field, T.G. 1999. Beef Production and Management Decisions. Third Edition.
Publ. Prentice Hill, New Jersey, pp 714.
Tattersfield, G.; Heuer, C.; West, D.M. (2006). Bull Soundness Examinations. Current
Research and Written Guidelines: Proceedings of the Society of Sheep and Beef
Cattle Veterinarians of the New Zealand Veterinary Association 36:123-126
Profitable Farming of Beef Cows
Chapter 4: Reproduction in the beef cow herd
70
Chapter 5: Cow health
Summary
Cattle are generally very healthy, but there are some animal health problems that can occur
in beef cows. This chapter deals with the more common areas.
Hypomagnesaemia or grass staggers is associated with low levels of magnesium in the
blood, which occurs in pregnant and/or lactating older cows. The incidence is relatively low
at 1 to 2% annually but major outbreaks can occur in individual herds.
Feeding and
management systems have been developed which can reduce the incidence of grass
staggers.
The essential elements of such systems are:
•
Calving to coincide with the onset of the spring flush of growth
•
Feeding cows well around calving (potentially at the expense of other stock classes)
•
Supplementation with magnesium
Facial eczema is caused by the mycotoxin called sporidesmin which is produced by the
pasture based fungus Pithomyces chartarum. The consequences of facial eczema range
from poor performance through to death, depending on the severity of liver damage. The
main risk period is after warm humid weather (usually between January and April) in the
North Island.
Control and treatment is achieved by monitoring and predicting danger
periods of high spore counts and or administering zinc salts. Facial eczema resistant stock
can be farmed in susceptible areas as resistance is relatively highly inherited.
Bovine Viral Diarrhoea (BVD) is a complex disease that affects cattle reproductive
performance. Around 65% of New Zealand beef cattle herds have active BVD infection,
and 80 to 90% of herds have had exposure.
BVD infection in adult cows can cause
reproductive wastage, weight loss and reduced milk yield. In young stock, BVD can result
in nil or poor weight gain, loss of body condition and the premature death of “Persistently
Infected” (PI) animals. Control is complex.
Other disease problems discussed include nitrate poisoning and bloat.
These occur
infrequently but can be very damaging and difficult to manage when they occur.
Profitable Farming of Beef Cows
Chapter 5: Cow health
71
TB in cattle is a disease of significant economic importance in New Zealand but is not
discussed in this chapter. (Refer Further Reading).
5.1
Grass staggers (Hypomagnesaemia)
5.1.1
Overview
Hypomagnesaemia (also known as hypomagnesaemic tetany or grass staggers) is a
nutritional disorder associated with low levels of magnesium in the blood. It is confined
mainly to pregnant and/or lactating cows, with clinical cases showing various gradations of
behaviour from a slightly disjointed gait and fine muscle tremors to violent convulsions and
sudden death. While surveys have shown that the incidence is relatively low, fluctuating
between 1% and 2% of cows annually, major outbreaks can occur in individual herds with
between 10-30% of the animals showing clinical signs or being found dead. The economic
importance of this disorder stems from both impaired productive performance in animals
suffering from hypomagnesaemia, and a high death rate amongst those affected by clinical
tetany. Though deaths from grass staggers can occur at any time from late autumn to early
spring, the greatest concentration of cases is usually over the calving period.
The disorder is related to a wide variety of nutritional, environment, and management
factors. These include: underfeeding, grazing lush spring herbage, abrupt changes in diet,
chemical composition of the feedstuff, fertilising practices, age and body condition of cow,
physiological state and a variety of stresses such as rough weather, handling, yarding and
trucking.
The
precise
physiological
or
biochemical
changes
involved
in
the
onset
of
hypomagensaemic tetany or grass staggers, and the reasons why many animals can
tolerate extremely low serum magnesium concentrations for long periods without exhibiting
symptoms, is obscure.
Under field conditions, the disorder frequently appears to be
triggered by stresses such as calving, oestrus, rough weather and excitation of animals
already with low magnesium levels because of diet. Feeding and management systems
have been developed which can reduce the incidence of grass staggers. The essential
elements of such systems are some or all of:
•
A timed mating period (7-9 weeks) to enable calving to coincide more closely with
the onset of the spring flush of growth
Profitable Farming of Beef Cows
Chapter 5: Cow health
72
•
During late autumn/winter, feeding cows at consistent levels to avoid sudden
changes in energy supply from one day to the next
•
Feeding cows to appetite on saved pasture from 2-3 weeks prior to the onset of
calving. While ad libitum feeding may not always be possible, feed supplies should
be manipulated and pasture allowances adjusted to provide intakes of at least
8 kg DM/cow/day. This saved feed may be costly unless the cow calves close to, or
on the spring flush
•
Supplementation with magnesium salts or oxide
Dietary changes (e.g. mature to immature herbage or pasture to hay and vice versa) appear
to be one of the most significant factors in inducing hypomagnesaemia and tetany under
farm conditions. Feed type changes frequently result in rapid and substantial falls in serum
magnesium concentrations and outbreaks of clinical tetany within 3-14 days, even under
apparently high levels of feeding.
5.1.2
Magnesium supplementation
Oral magnesium supplementation can be very effective in preventing grass staggers in beef
cattle.
Magnesium-rich materials most suitable for this purpose are magnesium oxide
(>50% Mg), Epsom salts (10% Mg) and magnesium chloride (11% Mg). The means of
administering magnesium supplement to beef cattle are:
Treated hay - Feeding hay or silage treated with magnesium oxide is one of the cheapest
and most effective means of administering supplementary magnesium. Care must be taken
to ensure that all cows receive their daily ration, that a minimum quantity of hay (<10
cows/bale) is used as a vehicle delivery mechanism, and that treated hay is eaten before
any untreated hay is offered.
Magnesium oxide (calcined magnesite or Causmag) should be mixed with water and
molasses at the rate of 50 g/cow/day and applied evenly along the cut edge of the bale.
The suspension must be stirred well before each dipperful is removed. For silage it can be
added as a powder to the silage wagon as it is being filled.
Magnesium oxide should never be applied to hay as a dry powder. Excessive wastage
inevitably occurs during feeding out, and the fine nature of the powder irritates the nasal
Profitable Farming of Beef Cows
Chapter 5: Cow health
73
membranes of cattle. The cows generally react by shaking the hay vigorously and dislodge
further quantities of the supplement.
Pasture dusting - Dusting pastures lightly with calcined magnesite (magnesium oxide)
prior to grazing is another very reliable method of ensuring that all cows consume at least
some supplementary magnesium.
The technique is particularly useful during sudden
emergencies, and where cows are being strip grazed on saved pasture.
Extensive trials have shown that dusting pastures at weekly intervals with ½ kg calcined
magnesite per cow can maintain serum magnesium levels close to or within the normal
range under a wide variety of weather conditions, pasture lengths and grazing pressures.
Calcined magnesite (60 mesh) is preferred to Causmag because it is slightly coarser and
will flow more readily through spinners and other topdressing equipment. The area to be
grazed in the coming week should be dusted early in the morning, when the dew on the
pasture will improve adhesion, and the area should then be ration grazed to prevent
physical agitation and dislodging of the calcined magnesite. Dusted pastures can tolerate a
fair amount of light rain, but should be re-dusted after heavy falls (more than 40-50 mm
within 2-3 days of application).
The pasture dusting technique tends to be more difficult to operate under extensive grazing
conditions. However, the method can still be very effective, providing application rates are
increased to ¾ to 1 kg calcined magnesite/cow/week. There is no real need to cover every
square metre of the area to be grazed. The material can be applied in strips, or smaller
areas dusted by hand each day.
Water trough treatment - Treatment of drinking water with soluble magnesium salts such
as magnesium chloride or Epsom salts at the rate of 60 g/cow/day can reduce the clinical
incidence of grass staggers and generally increases mean serum magnesium levels in
cattle by about 20%. The technique appears to be convenient and easy to operate, and for
that reason is fairly popular with farmers.
There are a number of factors which can
influence the efficacy of the technique, and a clear understanding of these is essential
before the method is adopted.
Cows must not have access to untreated water and the method is not one that can be
applied quickly. Cows need to be trained to accept the treated water at low concentrations
over a 2-3 week period.
The final treatment rate of 60 g/cow/day provides a lower
Profitable Farming of Beef Cows
Chapter 5: Cow health
74
magnesium intake than desirable, but is the best compromise possible given the palatability
and diuretic properties of these soluble magnesium salts.
The technique also tends to be unreliable because of wide variations in drinking behaviour.
Mean daily water intakes can range from above 40 litres/cow to less than 5 litres/cow
according to weather conditions, and the dry matter content of the feed. Under very wet
conditions many cows will go without drinking for up to two days. Water consumption is
usually higher and more stable on rations composed largely of hay and mature pasture.
The actual method of adding the magnesium salt to the drinking water is another factor
which can affect the success of the technique. Stripping of the material from the trough by
early drinkers can also be a problem where dilution is allowed to occur as the animals drink.
Under these circumstances the dose should be split and added on two or three occasions
during the day, or a trough dispenser used which allows a steady flow of material, and at
the same time provides for a wide range of water consumption.
Magnesium licks - Free access to magnesium licks may help limit the incidence of grass
staggers under extensive grazing conditions where other methods of supplementation
cannot be used. Animals need to trained to accept licks well before the critical period
commences, and variations in licking behaviour between animals, and by the same animal
at different times, can be an issue. Observations on licking behaviour of individual animals
show that about 10% of a herd can be classed as non-lickers, a further 10-15% as very
poor, and a small proportion as avid lickers who may consume excessive amounts and
show obvious signs of scouring. The remainder of the herd usually exhibit a marked cyclic
pattern of licking, with a number of animals licking vigorously for several days and then
showing no interest for periods of 5-10 days or more.
The cumulative effect of this
behaviour is that about 25% of the herd receives virtually no magnesium supplement, and
the serum magnesium concentrations in the remainder fluctuate widely.
Magnesium bullets – Probably the most costly method of supplementation, the use of
intra-ruminal slow release bullets can be very effective in extensively grazed herds.
Depending on the severity of magnesium deficiency in the diet, the bullets may only need to
be dosed into the older cows which are more prone to staggers.
The bullet remains
effective for about 4 weeks
Profitable Farming of Beef Cows
Chapter 5: Cow health
75
5.2
Facial eczema
Facial eczema is caused by the mycotoxin sporidesmin which is produced by the fungus
Pithomyces chartarum.
Sporidesmin is found almost entirely in fungal spores and is
primarily toxic to the liver.
Severe liver damage can occur.
Animals may exhibit
photosensitivity. The consequences of facial eczema range from poor performance through
to death, depending on the severity of liver damage.
Sheep are more susceptible than cattle primarily because they graze closer to the base of
the sward and hence ingest more of the fungal spores. The main risk period is after periods
of warm humid weather (usually between January and April) in the North Island.
The
periods of greatest risk occur when humidity is close to 100% and grass minimum
temperatures are above 12ºC for three nights or more. These conditions are found when
more than 4 mm of rain falls within 48 hours.
Most regions provide spore counting
information (some done by local veterinarians or farm consultants and reported in
newspapers, etc.)
Counts above 100,000 spores per gram of grass (wash method) are
considered dangerous. See “Further Reading” at the end of this chapter for reference to a
description of this spore counting method.
Control and treatment is achieved by:
•
Monitoring spore levels and predicting danger periods
•
Not grazing at-risk paddocks and ensuring cattle do not graze pastures too hard
•
Spraying pastures with fungicides to prevent fungal growth - costly but useful for
prevention for high value animals e.g. breeding or service bulls
•
Administering zinc salts - via drinking water, as a drench, or as a spray on pasture
•
Time capsules – rumen bullets which provide effective protection for 5 weeks after
being administered.
Refer ‘Further Reading’ for more details.
Profitable Farming of Beef Cows
Chapter 5: Cow health
76
5.3
BVD in beef cattle
Bovine Viral Diarrhoea (BVD) is a viral disease that affects cattle. Recent New Zealand
studies by Heuer and others (2008), have shown that BVD is extremely prevalent in beef
herds. Around 65% of New Zealand beef cattle herds have active BVD infection, and about
80-90% of herds have had exposure to BVD virus. Heuer and others found that between
mating and pregnancy testing, BVD could reduce pregnancy rates by an average of 5% in
herds that had active infection. The data also suggested that about 2% of New Zealand
beef cattle herds will experience a decrease in pregnancy rates of at least 15% due to BVD.
These figures do not include abortions that were not measured in this study
Besides reproductive wastage, BVD causes weight loss and reduced milk yield. In young
stock, (3-12 months age) BVD can cause a raft of ill effects, including nil or poor weight
gain, loss of body condition and the premature death of “Persistently Infected” (PI) animals.
BVD is also immunosuppressive; meaning cattle that have an active infection will have a
compromised immune system that cannot protect them from other diseases. BVD infection
has a major impact during mating and pregnancy. BVD causes infertility, embryo loss,
abortions (slips), stunted and deformed calves, and the birth of dead calves. BVD does the
most damage when it infects pregnant cows during early pregnancy. If a cow contracts
BVD while she is pregnant, she may give birth to a PI calf. PI animals spread the disease
and perpetuate it from one generation to another.
It can take as little as one hour of contact with a PI animal to transmit BVD virus to an
uninfected animal. Infection commonly occurs either through direct contact (nose to nose)
or ingestion of faeces containing the BVD virus. Other possible routes of transmission are
semen, milk, saliva, urine, placenta and birth fluid. It is also possible for the BVD virus to be
spread through cattle yards, stock trucks and to be carried around on footwear. The virus
can survive in the environment for up to seven days. Once contact has taken place the
virus replicates inside the epithelial cells and spreads as a free virus within infected blood
cells, penetrating different tissues in the body.
5.3.1
Persistently Infected (PI) animals
As the name suggests, a PI animal is one that continually sheds the BVD virus throughout
its life. Some PI animals can be recognised by vets and farmers as ‘poor doers’. These
animals often succumb at a relatively young age from a more severe form of BVD called
Mucosal Disease, or other diseases associated with BVD, e.g. pneumonia. It is estimated
Profitable Farming of Beef Cows
Chapter 5: Cow health
77
that about half of all PI cattle die within the first 12 months of life and 80% are dead by two
years due to the virus causing suppression of the immune system,. However, some PI
animals appear normal, survive longer than 18 months and act as long term carriers of BVD
virus, continuing to infect those naïve animals in the herd not yet exposed.
These PI
animals do not show obvious signs of illness and are difficult to recognise. They can breed
successfully but their progeny are always PI, thus perpetuating the disease in the herd.
Surviving PIs make up about 1% of the adult cattle population.
In dairy herds, calves – including PIs – are removed from their mothers, only to return to the
milking herd a couple of years later. This leads to a regular cycle of re-infection every few
years. However, in suckler beef herds, calves and cows are kept together allowing a much
more dynamic spreading of the disease, back and forth between younger and older
animals. This means that PIs can be in constant contact with susceptible new calves,
replacements, bulls and the breeding herd.
5.3.2
How does the virus affect cattle?
Calves may be sub-clinically affected and not show symptoms except perhaps reduced
liveweight gain. Other calves (3-12 months age) can show a range of symptoms including:
•
Reduced appetite
•
Nil or poor liveweight gain
•
Scouring
•
A rough coat and a loss of body condition
•
Coughing
•
Discharge from the eyes and nose
•
Ulcers in the mouth and between the toes
•
Premature death of PI animals
BVD is often characterised by high morbidity but low mortality. BVD in young stock is
frequently not diagnosed or miss-diagnosed because symptoms can be similar to
parasitism. Some farmers therefore mistakenly drench without getting a diagnosis. Since
most stock recover after a BVD infection, farmers often get the false impression that their
stock have responded to the parasite drench.
Profitable Farming of Beef Cows
Chapter 5: Cow health
78
Reproductive wastage occurs when a heifer or cow becomes exposed to BVD virus for the
first time when it is pregnant. The outcome depends on when the pregnant cow is infected
after conception:
•
0-45 days
Cow fails to conceive or loses embryo and returns to service (long returns)
•
45-125 days
Virus causes an abortion and return to service, or results in the birth of a PI
animal which may be sick, scouring, stunted or apparently normal
•
125-180 days
Virus enters the unborn calf, producing a variety of effects including abortion
and congenital deformities.
Introducing PI bulls to a herd during mating, especially a naïve herd, can be devastating
and very expensive. PI bulls are the biggest cause of introduced BVD infection in to a herd
and are a significant threat to the reproductive performance of beef breeding herds
PI breeding bulls affect reproductive performance through direct, horizontal spread of the
virus to BVD-free and heifers during breeding or pregnancy. Cows may be infected by
transmission of the virus directly into the reproductive tract during mating, which can affect
conception and fertility of the dam being bred; and through poor semen quality.
5.3.3
Control of BVD
To control the disease all breeding bulls should be blood tested prior to mating and certified
as BVD virus antigen negative and then vaccinated twice, three to four weeks apart, and
prior to mating. Vaccination will protect them from acquiring a transient infection from a PI
cow, heifer or calf with which they are going to be joined which could cause temporary
infertility.
Previously vaccinated bulls require an ongoing annual booster prior to each
mating.
Herd control options include eradication by blood testing all the herd (cows, calves, heifers,
steers, bulls), identifying the PIs and culling them. Then either adopt stringent biosecurity
measures that will prevent the herd getting re-infected or protect animals through
vaccination. In New Zealand, with large numbers of livestock, large farms, often many
neighbouring farms with livestock, lack of stock proof fences, frequent livestock movements
Profitable Farming of Beef Cows
Chapter 5: Cow health
79
off and on the farm, purchase of stock with unknown BVD status, biosecurity is often not
applicable or manageable. This leaves vaccination as the only practical option.
To reduce costs, some farmers elect to vaccinate without blood testing and eradication.
This way all BVD-free cows will be protected and any PIs in the herd will eventually die or
be sold. Over time, the herd should become BVD free. With the high incidence of BVD in
herds in New Zealand, a lot of older cows will be naturally protected, so a practical way to
start off is to vaccinate the heifers in the first year then follow them up with annual booster
vaccinations annually. Keep vaccinating the new crop of heifers each year, until eventually
the whole herd is vaccinated and protected.
5.4
Nitrate poisoning
High levels of nitrate and nitrite in plants and water sources are the primary cause of acute
nitrate poisoning in cattle. Plants which are the main source of nitrates for cattle (and
poisoning) include regrowth rape, choumollier, turnips, immature green oats, Italian rye
grass and young maize. Nitrate poisoning is rare on permanent pasture. Rapidly growing
plants, grown in nitrogen rich soils, after a period of drought, are most dangerous.
Nitrate poisoning in cattle is due to either ingestion of pre-formed nitrite, or to the conversion
of nitrate to nitrite in the rumen by micro-organisms. Severe loses can occur as a result of
sudden deaths, and abortions, in cattle consuming high levels of nitrate in their diet.
Treatment is with methylene blue administered intravenously.
Beef cows grazing regrowth crops or fresh herbage after a drought are especially
susceptible to high nitrate intake. Plants can be tested. A good handful of plant materials,
including the stalk, should be sent to an animal health laboratory.
5.5
Bloat
5.5.1
Overveiw
Bloat is not a common problem for beef cattle, but when it occurs, it can be very difficult to
manage. Its occurrence can be sporadic and hard to predict. Animals vary, genetically, in
their susceptibility to the problem and resistance is quite highly inherited. Bloat occurs
when stable protein foam develops in the animal’s rumen and cannot be belched out like
the normal rumen gases, which are constantly produced. The end result can be fatal,
Profitable Farming of Beef Cows
Chapter 5: Cow health
80
because of physical pressure on internal organs such as the heart, which eventually stops.
Bloat is most prevalent in early spring and where soil fertility and pasture quality are high. It
is more common, but not exclusively so, on pastures of high clover content. Bloat can also
occur on brassica crops and the new fast-growing grasses. Low fibre content seems to be
a factor.
In all bloat risk situations, adding fibre such as hay to the diet decreases the risk. When the
risk is very high, adding anti-bloating agents to water either in the water supply or as a
drench can be very effective, but the latter process is very tedious and impracticable in run
cattle.
Slow-release, Rumensin “bullets” are effective and are also reported to give a
liveweight gain response.
5.5.2
Management measures to reduce the risk of bloat
•
Ensure the animals are not hungry when they are introduced to dangerous pasture
•
Likewise, do not use strip grazing (behind a hot wire) on dangerous pasture. Strip
grazing creates the “hunger/eat ravenously” cycle
•
Provide fibrous feed, such as hay, as a supplement with dangerous clover pasture
to increase chewing time and rumen fill and reduce bloat risk.
5.6
•
If planting new pasture, use a balance of grasses and clover in the seed mix.
•
Plants with high tannin content (e.g. docks) reduce bloat risk.
Further reading
BVD website: www.controlBVD.org.nz. Established to help farmers and other interested
parties deal with BVD issues.
Heuer, C.; Tattersfield, G.; West, D.M.; Olson, W.O.
2008.
Effect of reproductive
pathogens on pregnancy rates in beef herds. Proceedings of the 38th Seminar of
the Society of Sheep and Beef Cattle Veterinarians NZVA, May 2008, pp 141-147.
Facial eczema spore counting: Appendices III and IV. In Profitable beef production, A
guide to beef production in New Zealand. A book, published by Meat & Wool
New Zealand, Beef Council. Third Edition. Meat & Wool New Zealand, PO Box 121,
Wellington.
Coddington, N. 2008. Cattle animal health, Ch 7 In Profitable beef production, A guide to
beef production in New Zealand. A book, published by Meat & Wool New Zealand,
Beef Council, Third Edition. Meat & Wool New Zealand, PO Box 121, Wellington.
Profitable Farming of Beef Cows
Chapter 5: Cow health
81
Chapter 6: Genetics of calf production from beef cows
Summary
Most of the beef cattle in New Zealand are managed in commercial herds, with bulls
purchased from outside the herd. Little or no individual recording is undertaken. A small
proportion of cattle are located in registered herds where pedigree recording with breed
societies has been mandatory.
These herds produce almost all of the bulls used in
commercial herds. There is a time lag before genetic benefits generated in the nucleus
(seedstock) herds are expressed in the commercial herds.
To be included in a genetic improvement programme a selection trait must be:
(1) economically important, (2) measurable, (3) heritable and (4) characterised by variability
in the population. The higher the heritability of a trait, the greater the proportion of the
parental genetic merit passed on to the offspring. Most of the growth traits in beef cattle
have a heritability of between 30% and 50%.
The other 50-70% of the measured
differences in performance (e.g. growth rate) between animals in a group, are due to
environmental factors.
The first step in the development of a breeding objective is to identify the goal; typically this
is profit oriented. Then, define a list of traits that influence the goal and to which economic
values for unit changes can be attributed.
In order to construct a single index value
encompassing several selection traits, economic values are needed for each relevant trait.
‘BREEDPLAN’ is a breeding programme widely used in beef recording in New Zealand and
Australia. It estimates the genetic merit, or breeding value of an animal from a number of
measurements made at various stages of the animal's life and from the performance of its
relatives. It reports estimates of genetic merit as Estimated Breeding Values (EBVs) for
each trait. EBVs are expressed as positive or negative deviations from a base which is set
at zero on a fixed date. The reliability of EBV estimates indicates the likelihood they will
change with the addition of more information over time. EBVs are a very powerful tool to
improve profitability.
‘BREEDPLAN’ also administers ‘BreedObject®’ (the Index System). It has a number of
advantages over EBVs. It uses a measure of profit per cow mated to genetically rank
animals and avoids the problem of trying to select animals based on an array of EBVs for
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
82
different production attributes.
BreedObject deals with all the difficult mathematical
calculations involved in making a genetic decision.
Growth rate is in most cases the primary selection criterion for beef cattle breeders because
it is easy to measure and is related to efficiency or economy of production. However,
breeders that select solely for growth rate need to be aware of correlated responses such
as increased mature cow weight resulting in increased feed intakes and increased birth
weight and calving difficulty.
The choice of breed for a particular farm will often involve compromises. Advantages of
different breeds can be attained by using sires with different attributes from dams, e.g.
Simmental bull mated to a Hereford x Friesian cow.
Crossbreeding is an established breeding method used in sheep and beef cattle breeding to
increase overall productivity through hybrid rigour. The challenge is to identify appropriate
crossbreeding systems that are simple and easy to operate in commercial beef breeding
cow herds. The use of composite breeds where 3, 4, 5 and up to 8 breeds have been
interbred to form a new breed is also a possibility.
6.1
Introduction
Most of the beef cattle in New Zealand are managed in commercial herds with bulls
purchased from outside the herd. Little or no individual recording is undertaken. A small
proportion of cattle are located in registered herds where pedigree recording with breed
societies has been mandatory.
These herds produce almost all of the bulls used in
commercial herds. Industry genetic change is dictated by the direction and rate of progress
achieved in the registered herds.
The number of new bulls required each year by the beef industry can be estimated by
considering the total beef cow and heifers in-calf (1,195,000 in 2008/09), the number of
cows or heifers mated by each bull (say 1 bull to 50 cows) and the average working life of a
bull (say 3 years). These figures suggest a total requirement of around 23,900 bulls and an
annual requirement of 8,000 bulls.
The way in which cows are split between bull-breeding registered and recorded herds and
commercial cow herds is often represented as a triangle (Figure 6.1). The bull breeding
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
83
herds (sometimes referred to as seedstock breeders) are at the top of the triangle and
commercial herds are at the base of the triangle where the majority of the cows are found.
Figure 6.1:
Diagrammatic representation of bull breeding herds and commercial herds
in New Zealand.
When genetic gains are generated in the nucleus (seedstock) herds, there is a time lag
before these genetic benefits are expressed in the commercial herds.
When a commercial farmer consistently buys bulls from a nucleus (or seedstock) breeder,
the commercial farmer's herd will, within the next 2-3 generations (10-15 years), be at the
same genetic level as the nucleus herd was when the bulls were bought.
generation delay is called genetic lag.
This 2-3
In the meantime, the breeder’s herd will have
continued to improve (Compare Client vs. Breeder A in Figure 6.2). This highlights the
importance of choosing the right nucleus breeder to buy bulls from. The most important
single factor in making that choice is that the breeder's herd must a have higher genetic
merit and rate of improvement than the commercial herd.
Figure 6.2 shows that the client who purchases bulls from Breeder A will progress at a
similar rate to Breeder A, although 2 generations behind. If bull breeder B or C were
chosen much less progress would be made.
The two generation lag can be reduced by purchasing, year after year, bulls at a level
above the average of Breeder A's bulls but the genetic gain in the commercial herd cannot
exceed that of the nucleus herd. It is likely that the above average genetic merit bulls will
also cost more, requiring the commercial producer to undertake a cost benefit analysis to
examine whether the reduced lag justifies the additional expense.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
84
Figure 6.2:
Genetic lag between commercial and bull breeding herds
An alternative to purchasing high genetic merit animals from bull breeders is to use
reproductive technologies such as artificial insemination (AI), multiple ovulation and embryo
transfer (MOET), and in vitro embryo production and embryo transfer.
Using these
techniques, the commercial breeder can access high value bulls (through AI) or high
genetic merit cows (through MOET). In theory the genetic lag could be reduced to about
5 years through use of AI, since only the genetic merit of the cows will lag behind the
nucleus. These technologies are not in common practice in the New Zealand beef industry
at present and are more likely to be used by breeders than commercial herds.
6.1.1
Selection decisions
Nucleus (seedstock) herds need to:
1. establish selection objectives and
2. generate genetic gains in objective traits
Commercial herds need to:
1. establish selection objectives
2. choose a breed mix
3. choose a seedstock breeder with the same objective
4. choose bulls consistent with objectives
5. choose heifer replacements in accordance with objective and
6. minimise the genetic lag behind the seedstock breeder
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
85
To be included in a genetic improvement programme a selection trait must meet four basic
criteria: (1) be economically important, (2) measurable, (3) heritable and (4) characterised
by variability in the population. Economic importance can mean different things to different
producers. For example a farmer selling weaners at 7 months of age will have slightly
different economic criteria to a farmer who breeds cattle and carries all progeny through to
slaughter. Objective measurement of beef cattle performance traits enables the breeder to
compare the traits irrespective of season, bias, year or environmental effects, and allows
the calculation of estimates of genetic merit. Liveweight is easy to measure and is a logical
first choice for most of the genetic improvement programmes.
Heritability is an important term.
It is defined as that proportion of the difference in
performance between individuals that on average is passed on to their offspring. So if the
heritability of a trait is high we can expect that much of the difference in performance of
parents will be passed on to their offspring. Conversely if the heritability is low only a small
percentage of this difference will be transferred. Heritabilities are expressed as proportions
(from 0 to 1) or percentages (from 0 to 100).
The higher the heritability of a trait, the greater the proportion of the parental genetic merit
passed on to the offspring. Most of the growth traits in beef cattle have a heritability of
between 30% and 50%.
This means that of the measured differences in growth rate
between animals in a group, 30-50% are due to genetic factors and 50-70% to non-genetic
or environmental factors. Carcass traits generally have heritabilities of between 30% and
55%. Female fertility traits tend to have much lower heritabilities of between 5% and 20%.
This means that a smaller proportion of the measured differences between animals for
fertility are due to genetic differences, and so the rate of improvement in fertility traits in a
genetic improvement programme will be slower than for the other traits.
Heritability
estimates for some of the important traits of beef cattle are shown in Table 6.1. Traits that
have greater variation, have more scope for change. Some traits vary more than others
and even if a trait has a low heritability, a large variation may mean that significant changes
can be made.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
86
Table 6.1:
Heritability estimates for some traits in beef cattle in temperate and tropical
environments Source: Adapted from Anon (2000) Note AA = Angus breed, BR = Brahman
breed, na = data not available.
Trait
Heritability
Description
Heritability estimate (%)
Temperate
(AA)
Tropical
(BR)
Reproduction
Conception
low
0-5
5-20
days-to-calving
low
0-10
0-10
calving ease (heifers)
low-medium
15-50
na
semen quality
low-medium
25-40
6-44
scrotal circumference (18 months)
medium-high
20-50
28-36
serving capacity (18 months)
low-high
15-60
na
maternal ability
medium
20-40
na
gestation length
medium
15-25
21
birthweight
medium
35-45
35-45
milk yield
medium
20-25
4
weaning weight
medium
20-30
3-50
200-day weight
medium
18
28
400-day weight
medium
25
37
600-day weight
medium
31
43
mature cow weight
high
50-70
25-40
carcass weight/day of age
medium
25-45
36
th
rib fat (12/13 rib)
medium
27
27
P8 rump fat
medium-high
29
18
Intramuscular fat (IMF%)
medium-high
15
30
eye muscle area (EMA)
medium
20-25
23
dressing %
medium-high
15
37
tenderness
high
4-25
16-30
retail beef yield (RBY%)
high
29
36
yield % carcass weight
high
49
52
25-50
25-50
na
25-36
Conformation and growth
Carcass
Other traits
temperament
medium-high
worm resistance
medium
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
87
6.2
Selection objectives
Selection or breeding objectives play an important role in the design of improved animal
breeding programmes as well as assisting with selection decisions involving a number of
genetic traits. In addition, breeding objectives are having an increasingly important role in
determining the acceptance and adoption of modern animal breeding technologies. Given
that the adoption of these technologies has been much greater in non-ruminants such as
pigs and poultry than it has been in some ruminants such as beef cattle, this latter point is of
considerable importance.
6.2.1
Breeding objectives
The first step in the development of a breeding objective is to identify the goal (e.g. superior
400 day weight). A breeding objective will reflect the production and economic objectives of
the individual.
The exception could be the bull breeder who may have a number of
objectives reflecting their own and their various clients’ objectives.
Given a clearly defined goal, the next step in the development of a breeding objective is to
identify traits that influence the goal and to which economic values for unit changes can be
attributed. A diagram of some possible economically-relevant traits is shown in Figure 6.3.
For a given situation, there may be alternative objective trait lists with different traits and
different definitions. Clear and precise definition of traits is very important. Correlations
between traits also need to be considered. For example, selection for yearling weight can
increase birth weight and in some cases increased calving difficulty. Selection on birth
weight can be used to limit correlated increases in calving difficulty. Highly sought after
bulls have low birth weight and high yearling weight breeding values.
Figure 6.3:
Some factors influencing profitability in beef cattle
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
88
6.2.2
Economic weights and values
In order to construct a single index value encompassing several selection traits, economic
values are needed for each relevant trait. Economic values should be defined as the net
benefit from improvement in an individual breeding trait in absolute ($ value) terms. This
value is expressed per unit change holding all other breeding objective traits constant. This
helps avoid the potential for double counting of benefits.
In many instances, "economic value" and "economic weight" are terms used
interchangeably. However, it is helpful to give economic weight a different definition. We
define here the economic weight as the benefit of improvement in an individual breeding
objective trait, expressed relative to some other trait of interest.
6.2.3
The importance of future prices
Many breeders are comfortable with the concept of profit (from the commercial farm
viewpoint) as the appropriate goal for a breeding programme. The question is, how does
one ensure that a comprehensive list of traits that influence profit is identified, and that the
economic values are appropriate?
Profit = income – feed costs – non-feed costs
Inspection of the above equation allows one to systematically break down the components
of income, feed costs and non-feed costs relevant to a particular farming circumstance.
However, there is a danger with this approach that one can focus on the economic and
management circumstances relevant to the current year, giving undue attention to present
rather than future determinants of income, feed and non-feed costs.
Consider the process of selection and mating that will occur in bull breeding herds in year 1.
The offspring will be born in the spring of year 2, with bull calves, sold as rising two-year
olds, for mating in year 4. These bulls will join with commercial cows in the spring of year 4
producing calves in the spring of year 5. If the farmer sells weaners, the first impact the
original bull breeding has on income will be in the autumn of year 6. If the farmer finishes
the male and surplus female offspring, this crop will be typically harvested in late year 6 or
in year 7. Bulls used for 4 breeding seasons will continue producing terminal offspring until
year 10. Where daughters are retained for breeding, they will have their first calves, if
mated as yearlings, in year 7. Cows may remain in the herd for 7 or 8 calvings, or until year
17 if the bull is used as a sire for 4 years.
Profitable Farming of Beef Cows
So, the impact of selection decisions in
Chapter 6: Genetics of calf production from beef cows
89
bull-breeding herds in year 1 will affect the commercial farmers’ income from year 6 until
year 17. It is therefore future circumstances that are important, not today's.
Breeders must consider the determinants of income, feed costs and non-feed costs in a
time-frame that extends at least 10 years beyond today.
Yet information on these
determinants will not be known with certainty by the breeder in year 1. Still these issues
must be considered and debated by breeders and farmers if they are to make informed
decisions as to their breeding objectives.
6.2.4
Selection criteria
Having established the selection (breeding) objective, the next step is to decide which
animals and which characteristics are going to be measured to help in predicting the traits
included in the objective. These characters are referred to as selection criteria.
Selection criteria can be defined as a subset of the characteristics of animals which can be
evaluated or measured and will form the basis of the criteria used to estimate the value of
breeding animals.
Selection criteria can be many and confusing!
For example, the
following factors may influence a commercial farmer’s decision to purchase a bull.
•
Price - can vary according to external factors
•
Breed
•
Appearance - e.g. coat colour, horns, conformation
•
Structural soundness - feet, legs, shoulders, jaw
•
Individual performance - weight of bull on sale day or weight gain up to sale day
•
Pedigree - sire and dam information
•
Genetic merit of bull - estimated breeding values (EBVs)
As was mentioned in the section on selection objectives, it is common for breeders to be
interested in improving several traits simultaneously. There are three methods of selecting
for multiple traits.
Tandem selection: This involves ranking animals for the most important trait and culling
on that trait. At some point in time, selection is relaxed on the first trait and imposed on a
second trait instead. Over time, selection proceeds through the list of traits in tandem. This
form of selection is the least effective as it is difficult to decide when to change from one
trait to the next, and if there are several traits, which is common in beef cattle production, it
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
90
will take considerable time before selection can be imposed on all traits. Another difficulty is
when two or more traits are unfavourably genetically correlated. In this case selection for
an increase in one trait will result in a correlated decrease in a second trait. On changing
selection from the first to second trait, there could be a related decrease in the first trait,
undoing some of the selection response achieved.
Independent culling levels: Selection using independent culling levels involves ranking
the animals for each trait in the selection objective. For each trait, some of the inferior
animals are culled. The relative importance of each trait will determine the extent to which
selection is imposed on that trait. Independent culling is widely used for culling animals on
conformation traits. For example heifers which have unacceptable feet or black Angus
cattle with white markings are likely to be culled regardless of their genetic merit for other
traits of interest.
Selection index: The selection index method to combines information from a number of
traits with known economic values so that animals can be compared. The selection index
method has not been used widely in the New Zealand Beef Industry, but is common in the
sheep and dairy industry. A new tool available through BREEDPLAN called BreedObject is
a selection index now available for New Zealand breeders.
6.3
Estimated Breeding Values (EBVs)
‘BREEDPLAN’ is a widely used breeding programme which estimates the genetic merit, or
breeding value of an animal using a number of measurements made at various stages of
the animal's life and the performance of its relatives. BREEDPLAN reports estimates of
genetic merit as Estimated Breeding Values (EBVs) for each trait. EBVs are predictions of
relative genetic merit, (what they will pass on to their progeny) not measures of the
observed differences between animals.
EBVs are expressed as positive or negative
deviations from a base which is set at zero on a fixed date.
EBVs are reported in the unit of original measurement, for example growth traits in
kilograms (kg), scrotal size in centimetres (cm) and days-to-calving (days); they are
expressed as deviations from a base average, which is set from a particular year for each
EBV.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
91
Group BREEDPLAN allows across-herd genetic evaluation of cattle from herds which are
linked genetically and have been recorded with BREEDPLAN.
EBVs are available for
growth, carcass, reproduction and other traits.
6.3.1
Growth EBVs
1. Birth Weight EBV: If recorded, the weight should ideally be taken immediately or
at least within a few days of birth. Birth weight is associated with an animal's weight
at later ages: in general, calves which are heavier at birth tend to be heavier later in
their life. An EBV for birth weight is not available unless the calf's birth weight or
that of a number of its relatives has been measured, although it may be estimated
with reduced accuracy from later weights such as weaning weight. Buyers looking
for easy calving bulls can use birth weight EBV as a guide, but should look carefully
at the accuracy of the EBV.
2. 200-day growth and 200-day milk EBVs:
These EBVs are derived from the
records of calves weighed between 81 and 300 days of age. The 200-day weight
(the measure of pre-weaning gain) is derived or influenced from three sources:
•
the calf's inherent growth potential
•
the dam's merit for milk production and milk quality
•
performance of all known relatives e.g. sire, dam, brothers and sisters.
The 200-day growth and milk EBVs are calculated for the 'growth' and 'milk' genes.
Note that the milk estimate in kilograms is not the yield of milk of the dam, but the
growth rate in the calf attributable to the dam’s milking ability. It is an indirect
measure of the milk production of the dam expressed in kilograms of calf weight at
200 days. It should be used in the selection process, if the contribution of the dam
through her milking ability, is important in a particular production system.
Each time a 200-day weight is recorded it increases the reliability of the EBVs for
growth and milk of all relatives of the particular calf. An EBV for milk in a calf is
simply a calculation of the average of its sire and dam's EBV for milk and is called a
mid-parent value or average. It is not until females have progeny, and males have
daughters that have weaned calves, that the EBVs for milk will change from the
average of their parents' EBVs.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
92
The heritability of 200-day milk is about 8%, which means that genetic progress in
this trait will be slow. Conversely, the heritability for 200-day growth is about 20%,
which enables greater opportunities in improved growth following selection using
this trait. Since EBVs for milk are less heritable than growth EBVs, they are more
likely to fluctuate as new information is added relative to growth.
3. 400-day yearling weight EBV:
This EBV covers records of calves weighed
between 301 and 500 days of age. This EBV is most useful for selection in yearling
production systems in which cattle are sold some months after weaning.
4. 600-day final weight EBV:
Final weight EBVs are computed for growth and
recorded between 501 and 900 days of age. It is an estimation of an animal's ability
to continue to grow to an older age.
5. Mature cow weight: This is defined as the cow's weight recorded at the same time
as her calf is weaned. The mature cow weight EBVs are estimates of the genetic
differences in weights between cows at weaning during production of their first four
calves. Mature cow weight EBVs for sires are based on weights recorded from their
daughters (following weaning of their calves) plus the correlations that exist between
cow weight and earlier growth performance. Mature cow weight EBV values can be
used to influence the mature size of the females in the herd.
6.3.2
Reproduction EBVs
1. Scrotal size EBV: This is adjusted to 400 days. An animal with a greater scrotal
size EBV will produce male progeny with relatively larger scrotal circumferences and
daughters that reach puberty at an earlier age. The sons of bulls with larger scrotal
size will on average have greater daily and total sperm production, which can be
associated with increased fertility. There is also a negative relationship between
scrotal size and days-to-calving of the female progeny, i.e. daughters will have
fewer days to calving.
2. Days to calving: This EBV is an estimate of the genetic differences between cows
in fertility, expressed as the number of days for the period from when the bull is
placed with the females to calving. A female with a shorter days-to-calving EBV
tends to reach puberty earlier as a heifer, return to oestrus earlier after calving and
conceive early in the joining period. A lower days-to-calving EBV value indicates
greater opportunity for the cow to conceive within any one mating period. Cows that
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
93
do not calve are given a 'penalty' figure. These EBV values for bulls are based on
the performance of their daughters and female relatives.
3. Gestation length EBVs:
These are estimates of genetic differences between
animals in the number of days from the date of conception to the calf birth date.
Gestation length EBVs are expressed in days. Gestation length is available only
when the conception date is known, that is, in the case of artificial insemination.
Gestation length is one component of days-to-calving.
An animal with a more
negative EBV will have progeny with a shorter pregnancy, more time to get back in
calf relative to females with a larger EBV, and potentially a smaller calf.
4. Calving ease: This EBV indicates the degree of difficulty experienced by the dam
at birth. The direct calving ease EBV is an indication of that animal's ability to calve
easily. Its components include gestation length and birth weight. Calving ease
maternal is the EBV associated with the daughter's ability to calve. A larger positive
value for both direct and maternal calving ease EBV, is a desirable selection option.
Birth weight EBV is a commonly used proxy for calving ease because it is a more
available statistic.
However, it does not predict calving ease as accurately as
calving ease EBV.
6.3.3
Carcass EBVs
Five carcass EBVs are available based on live animal ultrasound scan measurements taken
by accredited scanners and information collected from actual carcass data. The measures
are eye muscle area, rump fat depth, rib fat depth, intramuscular fat % (IMF%) and retail
beef yield % (RBY%). Extra data collected at abattoirs, (including hot carcass weight,
marble score, meat colour, fat colour and meat pH) can be stored on the database. The
quality EBVs are expressed in terms of a 300 kg dressed steer carcass weight and
measured between 300 and 800 days of age with a preference for measuring at less than
two years old.
1. Carcass weight: These EBVs are estimates of the genetic differences between
animals' untrimmed hot carcass weight at 650 days of age and are based on
slaughter carcass weight records.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
94
2. Fat depth: This can be readily measured at the 12/13th rib site and the P8 rump
site on a standard 300 kg carcass. The measurement at the 12/13th rib has a
genetic correlation of 0.9 with P8 fat and is utilised in the multi-trait model to refine
the EBV for P8 fat. Fat depth has a negative relationship with retail beef yield.
3. Eye muscle area (EMA): This is measured in cm2 at the 12/13th rib on a standard
300 kg carcass. Eye muscle area and fat measurement are used in the prediction
of retail beef yield % from a live animal or carcass. Larger eye muscle area EBVs
are associated with higher carcass yield and often with leaner carcasses.
4. Retail beef yield (RBY %): The major reason for measuring either fat depth or eye
muscle area is to predict the yield of meat from the live animal or carcass.
Equations have been developed for the within-breed calculations of retail beef yield
percentage. These include age, liveweight, fat depth and eye muscle area with fat
depth having a greater influence than eye muscle area. Retail beef yield % EBVs
can be used to select for yield of retail cuts for carcasses.
5. Intra-muscular fat (IMF %): This is a measurement of the percentage of fat within
the 'eye muscle' and is similar to 'marbling score' as reported at slaughter. 'Marbling
score' is a subjective assessment of intramuscular fat. IMF% is based on a 300 kg
standard carcass. IMF% EBVs are important in the selection of sires to produce
progeny for markets that require increased amounts of marbling in carcasses (e.g.
Japan).
6.3.4
Additional EBVs available
1. Feed efficiency: Net feed intake EBVs can be used to predict the differences in
feed consumption among progeny of different sires adjusted for differences in their
growth performance. Net feed intake is sometimes referred to as residual feed
intake (RFI), net feed efficiency (NFE) or net feed conversion efficiency (NFCE). A
negative net feed intake EBV is preferred. Recording for this EBV is expensive and
is available in Australia but not yet New Zealand.
2. Other traits: A number of traits are being analysed according to demand. This
varies between the breed societies that use BREEDPLAN.
Traits available for
analysis may include: animal length records (e.g. hip height), conformation records
(e.g. leg score), temperament records (e.g. flight speed) and parasite records (e.g.
tick score).
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
95
6.3.5
Accuracy of EBVs
There are benefits in knowing the reliability of EBV estimates and the likelihood they will
change with the addition of more performance information about the animal or its relatives.
Accuracy is expressed as a % and is calculated from the number of performance records
that are available for each trait on the animal itself, as well as its progeny and relations
(Table 6.2).
The higher the accuracy, the greater the confidence that the EBV is an
accurate estimate of the animals’ true breeding value, and the less chance of it changing as
more information becomes available.
An accuracy of less than 55% indicates that no direct information is available about the
animal.
Information may come from relatives rather than direct observation or from a
correlated trait. An EBV with this level of accuracy should be considered a preliminary
estimate only and could change considerably up or down as more substantial information
becomes available.
Table 6.2:
Accuracy values for a trait (assumed heritability 30%) when additional
performance records are added to an EBV.
Performance measured on:
Accuracy (%)
Individual
55
Individual + 10 PHS* + 2 MHS
61
Individual + 20 PHS + 4 MHS
64
10 progeny
67
32 progeny
85
55 progeny
90
Individual + 10 progeny
74
Individual + 20 progeny
82
Individual + 45 progeny
90
* PHS: paternal half sibs or other calves by the same sire, MHS: maternal half sibs or other
calves by the same dam.
EBVs for yearling bulls without progeny recorded are calculated from the record of the bull
and/or its relatives. The accuracy of these EBVs will be in the range of 40% to 75%, with
the higher accuracy EBVs reflecting greater information from relatives. The EBVs of sires
with recorded progeny are more accurate and more stable than the EBVs of bulls without
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
96
progeny.
Progeny information is a better estimate of a bull's breeding value than the
individual's performance. These EBVs will range in accuracy from 75% to 99%, with the
higher accuracy EBVs reflecting a greater number of progeny and/or the availability of
daughters' progeny records.
6.3.6
Profitable use of EBVs
EBVs are a very powerful tool in selecting animals to improve profitability for both breeders
and commercial buyers. For example, the progeny of bulls in the top 1% of the Angus
breed for carcass weight generate 17.5 kg more carcass weight at 22 months of age than
bulls in the bottom 1% (1999 NZ Angus Genetic Evaluation Report). This demonstrates an
important aspect of EBVs. That is, the more highly ranked the animal is in the breed, the
greater the genetic progress and the more profit the bull will generate. Therefore a buyer
can afford to pay more for highly ranked bulls. Percentile bands show where a particular
animal ranks within a breed for a specific trait.
Different types of animals are needed to fit the various performance levels of existing herds
and suit the range of market requirements in the beef industry. EBVs from BREEDPLAN
can be used to select or buy bulls to improve different systems. For example, growth
figures for five bulls are shown in Table 6.3.
Table 6.3:
EBVs Group BREEDPLAN (kg) for several growth traits for five bulls.
Birth
Weight
200-day
milk
200-day
growth
Yearling
weight
Final
Weight
1
-1
+5
+10
+30
+45
2
+2
+2
+14
+25
+28
3
+5
-8
+16
+40
+50
4
+2
+10
+10
+25
+30
5
+1
+2
+10
+28
+40
Sire
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
97
Selection of a sire will depend on what production system the farmer operates as
demonstrated in the examples below.
Buyer 1 sells weaners and does not retain any heifers, choosing to buy in replacement
females. The breeder places most emphasis on EBV for weaning weight, while trying to
avoid large birth weights. The most likely choice is Sire 2 (sire 3 is rejected because of +5
for birthweight).
Buyer 2 sells weaners but also breeds their own replacement heifers. The breeder thinks
that increasing the level of milk production in the herd would be profitable. Sire 4 is the
most likely choice because of its emphasis on milk and early growth rate.
Buyer 3 wants to increase yearling and final weights, avoid calving difficulty and slightly
increase milk production. The main product is steers to finished weights and the breeder
retains replacement heifers. The most likely choice would be Sire 1.
Buyer 4 breeds straight-bred animals in a harsh environment where cows with high EBVs
for milk are known to be slower to rebreed. The breeder wants to maintain the current
levels of birth weight and milk production while increasing growth rate in two year old cattle.
The most likely choice would be Sire 5.
6.4
Index Selection (BreedObject)
BreedObject® (the Index System) is also administered by BREEDPLAN and has a number
of advantages over EBVs. Any worthwhile genetic selection programme should target profit
as its goal, however most EBVs are only indicators of potential to make profit and do not
directly influence it. For example, you do not get paid directly for the milking ability of a beef
cow (200 Milk EBV), however it does contribute to the survivability and growth of the calf.
BreedObject uses a measure of profit per cow mated to genetically rank animals. The
presence of so many EBVs makes the selection process very confusing because buyers
often do not know which EBVs to target or how to financially prioritise them. Also, buyers
cannot account for the impact of genetic correlations (relationships) existing between traits.
BreedObject ranks the bulls using easily understood and meaningful criteria, i.e. dollars per
cow mated, and presents just one genetic selection figure – EBV for profit as the index
measure.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
98
6.4.1
Angus BreedObject
The Angus breed for example has three BreedObject indices: the Self-Replacing Index, the
Ease of Calving Index and the AngusPure Index.
1. The New Zealand Angus Self Replacing Index
The Angus Self-Replacing Index ranks bulls on their progeny’s ability to generate profit
(profit per cow mated) in a self-replacing herd situation in which some females are
retained for breeding and surplus females, along with all males, are slaughtered. The
main drivers of profit included in the Index (in order of economic importance) are:
•
Direct and Maternal Calving Ease
•
Growth
•
Meat Yield
•
Cow Survival
•
Finishing Ability
•
Fertility
•
Cow Efficiency
In short, selection on this Index is expected to favour production of a cow herd with
excellent reproductive efficiency, rearing progeny with moderate-to-high growth rates
and high yielding carcasses.
2. The New Zealand Angus Ease-of-Calving Index
The Angus Ease-of-Calving Index ranks bulls on their progeny’s ability to generate profit
(profit per cow mated) when crossed with dairy cows and heifers to produce dairy beef
progeny. While calving ease is by far the most important profit driver in the Index,
growth and to a lesser extent meat yield also contribute. This Index is also a reasonable
indicator of a bull’s suitability for use over beef heifers.
3. The AngusPure Index
The beef production system that this index targets is the same as for the self replacing
index but has a greater emphasis on higher marbling sires with progeny sale at around
16-17 months of age.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
99
6.4.2
Hereford BreedObject
There are three breed-specific selection indexes for Hereford cattle:
1. Export/Maternal Index – This focuses on the production of a 555 kg steer by age
20 months from a self replacing cow herd (that is, a herd producing females over a
5 year period to continue the breeding policy).
2. Hereford Prime/Maternal Index – This focuses on producing a 510 kg steer by age
18 months.
3. Dairy/Maternal Index – This aims to produce readily marketable crossbred steers
at 475 kg by 16 months, but is also useful for people breeding Hereford x Friesian
cross heifers for beef cows.
In Table 6.4, the ‘target market’ represents the production system or market to which the
Index Value and the Breed Average Index Value relate.
Before selecting a bull using the BreedObject Index system, the buyer must determine
which Index best represents the production system or target market that he/she is most
likely to be using or supplying. Table 6.4 displays three such scenarios; the Hereford
Export/Maternal, the Hereford Prime/Maternal, the and the Hereford Dairy/Maternal. Having
decided which Index to use, the next step is to select the highest ranking bull available
within this Index.
As long as the animal is structurally and reproductively sound, the
balance of EBVs that make up the Index should be acceptable.
Table 6.4:
Examples of BreedObject selection index values for an example bull vs. the
breed average.
Target market
$ Index Value
Breed Average
A
Export/Maternal ($)
+$44
+$34
B
Hereford Prime/Maternal ($)
+$54
+$40
C
Dairy/Maternal ($)
+$34
+$20
A bull buyer producing heavyweight carcasses for export would most likely target Bull A in
Table 6:4 with an Index value of $44. Note that the Hereford breed average for this Index is
$34. If Bull A and an average bull for this Index were each mated randomly to 160 cows
during their lifetimes, Bull A would be expected to produce $800 ( ($44-34)/2 x 160 ) more
profit during his lifetime than an average bull with an Index of $34. Therefore the buyer
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
100
could afford to pay $800 more for Bull A than an average bull and still be just as financially
well off. Remember, the profit difference between the two bulls must be divided by 2
because the bull only supplies half his offspring’s genes.
6.5
Selecting breeding females
The most rapid progress in genetic improvement of a beef herd is achieved through
accurate and effective bull selection. On average, each sire passes his genes onto about
50-150 calves during his working life, while each female passes on her genetic make-up to
only 5-10 progeny in her lifetime.
However, although commercial breeders should be
concerned mostly with bull selection they still need to make decisions on which heifers to
retain as replacements in their herd.
Selection of breeding females can increase the level of desirable traits in the herd. Through
female selection, producers can improve fertility, weight of calf weaned, the subsequent
growth of weaned animals and the ultimate value of the sale animals through carcass
quality etc. Improvements in fertility and survival will increase sale numbers. Selection for
environmental adaptation, growth rate, temperament, structural soundness and carcass
traits will affect the price achieved or the relative value of sold animals. Factors such as
environmental adaptation, including resistance to diseases and parasites, and higher
growth rates will affect the cost to produce each animal to sale weight. There are three
opportunities to select females: pre - and post-mating and at first weaning.
selection removes poor performers from the herd.
Pre-mating
Selection either allows culls to be
replaced by more productive females, or allows the remaining productive animals access to
more feed.
Pre-mating selection
The number of replacements required for a beef cow herd is determined by:
•
current herd reproductive performance;
•
herd policy for culling and selection
- culling for age
- culling for reproductive failure
- culling for non, or poor performance in other production traits;
•
maximum cow age;
•
annual culling and mortality rates.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
101
Higher reproductive rates allow increased culling for performance and/or a lower heifer
retention rate. Some farmers mate excessive members of heifers and treat surplus animals
as meat producing “once-bred-heifers”.
At this stage only those heifers with obvious bad temperament, structural faults or low
growth rates that will severely impede their survival or their ability to reproduce and grow
should be culled. The remainder of the heifers should be mated for a sufficient period and
the required number of pregnant replacements retained.
Post-mating selection
Post-mating selection is primarily concerned with identifying productive females. Selection
here is on pregnancy test.
Selection at first weaning
There are a limited number of times during the year that cows can be evaluated for
productivity (e.g. kg calves weaned / kg cows mated). The best times are at weaning and
during pregnancy testing. Culling criteria might include:
•
Fertility: Failure to become pregnant, particularly if not lactating, and failure to
produce a live weaner are the most critical criteria. In some intensively managed
herds with a short-period of calving, cows that produce lighter or lower quality calves
may also be culled.
•
Structural soundness: Culling for unacceptable temperament and structural faults
such as malformed teats should be on-going during the life of the female.
•
Mothering ability: Mothering ability is the female's ability to feed and look after her
calf. Some females will abandon a calf after birth or become separated from the calf
later on. The ability to protect the calf from predators is also a factor in mothering
ability. Culling cows that fail to wean a calf removes poor mothers.
•
Cow efficiency: This is based on calf weaning weight relative to cow weight. This
requires calves to be identified with their dams, therefore, most farmers do not
select for cow efficiency because of the practical difficulties of doing this.
See
Chapter 2 for more details.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
102
6.6
Evidence of genetic progress
Growth rate has been and remains the primary selection criterion for most beef cattle
breeders because it is easy to measure and is related to efficiency of production. Research
at several locations around the world has shown that selection for high (low) growth rate
produces heavier (lighter) animals than random-bred controls. In one trial in USA, genetic
progress continued for 65 years of selection in Hereford cattle, although responses are
diminishing primarily due to decreasing generation interval.
The best New Zealand example comes from an experiment established in 1971 on hill
country at Waikite near Rotorua (Baker and others (1990) and Morris and others (1992)).
This experiment had three closed herds (no outside genetics introduced) of Angus and
Hereford selected for (1) adjusted 13 month weight, (2) 18 month weight and (3) random
selection. Annual responses in liveweight in the selected herds were 0.48% to 0.96%
greater than in the randomly selected control herds. This is an actual difference of up to
1.06 to 2.12 kg/year over the 14 year period of calvings.
One of the frequently asked questions is what were the associated or correlated responses
in other traits while this single selection for growth rate was occurring? Six correlated
responses were observed in the Waikete trial.
1. Cow weight - selection for yearling or 18 month weight resulted in mature cows that
were 7.5% and 8.2% heavier respectively than the randomly selected control herd.
2. Calf birth weight – selection for growth rate increased birth weight
3. Scrotal circumference - selection for yearling weight or 18 month weight increased
scrotal circumference.
4. The selected herds were taller as measured by height at withers.
5. Intake was measured in a sample of bulls after 11 years of selection and the
13 month and 18 month selected bulls had silage intakes that were 10.4% and
11.7% greater than the control or randomly selected bulls.
6. In a separate experiment, sires from the selected herds (after 6 years of selection)
were mated to balanced samples of test cows. Weaning weights from the herds
created by using sires from the yearling (13 month weight) and 18 month weight
selected herds were superior by 8.6 kg (5.7%) and 2.2 kg (1.5%) than weaning
weights from cows sired by randomly selected bulls.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
103
Breeders that select solely for growth rate need to be aware of correlated responses in cow
traits such as increased mature cow weight resulting in increased feed intakes, increased
birth weight and calving difficulty. Selection for growth rate resulted in females reaching
puberty earlier. Reproductive rate was similar between the lines.
A subsequent trial (Morris and others 2006) recorded a difference of 70 days ± 6 days in
age at puberty between ‘early’ vs. ‘late’ puberty selection lines (a difference of 17%).
Genetic correlations between age at puberty in heifers and cow reproductive traits were
favourable so that selecting heifers for earlier pubertal age would improve cow reproduction.
In reality, selecting heifers for puberty is not practical. The correlated response in age at
puberty for heifers and scrotal size in half brothers was high. Selecting on scrotal size
would be a more practical way to decrease age at puberty.
In summary, evidence suggests that selection for growth will result in rapid progress but
gains in selection for reproductive traits, while positive will be less spectacular.
Evidence of benefits from selection for carcass and meat traits have not been demonstrated
in New Zealand. Examples are available from other countries to suggest the practice is
worthwhile if producers are paid for the improvement. Presently farmers in New Zealand
are mainly rewarded for carcass weight and as final weight is the main determinant of
carcass weight, selection for growth remains the primary objective in most breeding
programmes.
6.7
Choice of breed
Breeds differ in their performance attributes for maternal traits (important in breeding cows)
and growth and carcass characteristics (important in finished cattle). The choice of breed
for a particular farm will often involve compromises. Sires with different attributes from
dams can be used to produce calves that exhibit traits from both breeds. An example is a
large sire over a dairy cross beef cow, e.g. Simmental bull mated to a Hereford x Friesian
cow.
Breed comparison trials were undertaken by the Ministry of Agriculture and Fisheries (MAF)
during the 1970’s. The performance of female crossbred progeny (except Angus which
were pure-bred and used as baseline for rankings) in these trials is shown in Table 6.5.
The crossbred cows were bred as yearling heifers to Angus and Beef Shorthorn sires. As
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
104
cows, they were subsequently bred to either Blonde d’Aquitaine, Charolais, Limousin,
Maine Anjou, Murray Grey or Simmental sires. Table 6.5 demonstrates that productivity of
the breeding cow up until weaning depends upon both high calving rates and high calf
weaning weights. The reduced age at puberty of dairy cross animals led to higher calving
rates as 2 year olds and improved productivity rankings.
Table 6.5:
Performance of crossbred (crossed with Angus or Hereford) cows.
Source: Morris and others (1993).
Puberty
(days)
% cows
Pregnant
% calves
born alive
% calves
weaned
Productivity1
(kg)
Efficiency2
(kg)
3
Angus
395
84
93
73
110
29
Jersey
339
87
96
78
141
38
4
382
85
91
74
118
29
Friesian
347
88
95
79
150
36
Limousin
Blonde
Aquitaine
South Devon
423
75
95
68
107
27
417
78
94
68
110
26
398
80
96
73
130
31
Maine Anjou
394
83
93
74
128
30
Simmental
393
79
93
69
123
29
Charolais
418
77
93
67
116
27
Chianina
432
73
95
63
102
24
Sire of cow
Hereford
1
Productivity = weight of calf weaned/cow joined
2
Efficiency
= weight of calf weaned per 100 kg of cow liveweight mated.
3
Angus x Angus
4
Hereford x Angus
The breed rankings in Table 6.5 are similar to results from other breed comparison trials
conducted elsewhere in the world.
Earlier trials involving at least 12 sires per breed compared the weaning and carcass
weights of crossbred progeny from Angus or Hereford dams. These results are shown in
Table 6.6 and demonstrate the effect of breed of sire on the calf. That is, calves sired by
breeds with larger mature size tended to have higher weaning weights and the highest
carcass weights.
Furthermore, these larger sized sire breeds tended to have leaner
offspring when harvested at a similar age.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
105
Table 6.6: Effects of breed of sire on carcass traits in animals at 31 months of age.
Source: Baker and others (1990); Morris and others (1990. (Dams are either Angus or
Hereford cows.)
Breed of sire
Weaning
Weight
(kg)
Preslaughter
weight (kg)
Hot
carcass
weight (kg)
Dressing
%
Fat
depth
(mm)
Muscle
longissimus
area (cm2)
Maine Anjou
173
562
294
52.4
5.4
104
Simmental
174
540
278
51.5
4.5
96
Friesian
167
561
287
51.4
7.1
93
Charolais
171
550
290
52.9
5.4
106
South Devon
168
550
284
51.9
7.4
97
Chianina
166
523
278
53.3
6.2
99
Blonde
Aquitaine
167
544
289
53.2
5.4
103
Limousin
160
515
273
53.3
5.4
103
Hereford1
159
504
264
52.5
9.8
91
Jersey
147
505
252
50.3
8.1
88
Angus2
151
489
248
50.9
7.6
91
1
Hereford x Angus
2
Angus x Angus
The animals from these breeds available in New Zealand in 2005 may differ in performance
from those used in the original MAF trials. However, the important messages from Tables
6.5 and 6.6 are that the breeds and their crosses can differ considerably in performance
attributes and no one breed excels for both maternal and growth characteristics.
The relative ranking of breeds and their crossbred progeny may change from one
environment to the next (Table 6.7).
The performance of some highly productive cow
breeds can decline as feed conditions deteriorate. It is therefore important to ensure that
potentially productive cows can be fed accordingly, otherwise production may fall
dramatically.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
106
Table 6.7:
Efficiency of beef breeding cows (weight of calf weaned/100 kg cow
liveweight mated in two environments. Source: Morris and others (1993).
Waikato flat
Rotorua Hill
Hereford x Angus
29
29
Friesian x Angus
36
35
Simmental x Angus
33
27
Limousin x Angus
28
25
Breed differences have been evaluated more extensively in the Germ Plasm Evaluation
(GPE) program at the U.S. Meat Animal Research Center (MARC) located at Clay Center,
Nebraska. More than 26 different sire breeds have been evaluated in seven cycles of the
GPE program (Table 6.8).
Females produced by these matings were all retained to
evaluate age and weight at puberty and reproduction and maternal performance through to
7 or 8 years of age.
Table 6.8 presents data for breed crosses grouped into several
biological types based on relative differences in growth rate and mature size, lean-to-fat
ratio, age at puberty, and milk production
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
107
Table 6.8:
Breed crosses grouped into six biological types on the basis of four major
criteria showing relative rankings.
Source:
Adapted from MARC Research Progress
Reports.
Although the information in Table 6.8 is useful, it should not be considered the final answer
to deciding which breed to use. A producer needs to recognise that the information in the
table reflects breed averages; individual animals and herds within the same breed can
perform better or worse than the average ranking shown.
6.8
Breeding systems
There are two basic breeding systems. If the source of replacement females is heifers
produced in the herd this is a self-replacing system. If heifers are not used as replacements
this is a terminal system.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
108
A self-replacing system produces its own replacement females but requires externally
selected sires. Since replacement females are retained in this system, the cow herd has
genetics from both herd sires and herd dams. Therefore, if herd sires have traits that are
undesirable in cows, they will continue to be exhibited; they cannot be hidden in a
self-replacing system. Both sires and dams in these systems should be similar in important
traits, without any undesirable characteristics.
In a terminal system, both replacement females and sires come from external sources.
However, since heifers produced in terminals are not retained for breeding, there is more
flexibility in choice of genetic types. Specialised maternal and sire types can be used in
terminals, since undesirable traits are generally not exhibited.
6.9
Crossbreeding
Crossbreeding is an established breeding method used in sheep and beef cattle breeding to
increase overall productivity through hybrid rigour. However, not all crossbreeding systems
are able to maximise these potential gains, because some are too difficult to implement
under commercial hill country conditions, especially in small herds. The challenge is to
identify crossbreeding systems that are simple and easy to operate in commercial beef
breeding cow herds. Crossbreeding does not replace the need for continued selection on
performance; rather, it adds to these benefits.
Crossbreeding by commercial beef cattle farmers may be practised for the following
reasons:
•
to introduce a new breed
•
to take advantage of the superior qualities of two or more breeds
•
to combine the qualities of the different breeds
•
to take advantage of hybrid vigour
•
to make maximum progress in the traits of low heritability
The benefits resulting from crossbreeding are best achieved through increased fertility of
crossbred cows and growth rate of calves. In Figure 6.4, it can be seen that if straightbred
cows reared crossbred calves rather than straightbred calves, on average, there would be
an extra 8.5% increase in weight of calf weaned per cow mated (e.g. for a 200 kg weaner
this would equate to 17 kg of extra calf weaning weight). If crossbred dams were then used
to rear the crossbred calves, a further 14.8% increase could be expected as a result of the
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
109
better maternal environment (due primarily to better fertility and milk production) provided by
the crossbred dams. Using crossbred dams to rear crossbred calves, the expected extra
calf weight weaned/cow would be 23.3% compared to straightbred cows rearing
straightbred calves.
Figure 6.4:
A comparison of percentage increase in calf weight weaned/cow exposed to
breeding, as a result of mating either straightbred cows to bulls of a different breed (centre),
or mating first cross cows to bulls of a third breed (right). The results were obtained from an
experiment involving all relevant crosses among Hereford, Angus and Shorthorn cattle.
Source: Taylor and Field (1999).
6.9.1
Alternative crossbreeding systems
As stated earlier, the maximum benefits from crossbreeding are obtained when using a
crossbred cow mated to a terminal sire. The following crossbreeding systems are suitable
for New Zealand beef cattle producers:
1. Purchasing crossbred heifer replacements
By buying-in all heifers, all of the cows in the herd can be mated to a terminal sire.
This results in maximum heterosis of about 23%.
A common system used by
farmers is the purchase of Beef x Dairy cross heifers (Hereford x Friesian or
Angus x Friesian) as weaned calves. These are mated at 15 months to an easy
calving sire breed (e.g. Angus, Hereford, Murray Grey, Shorthorn) and from then on
to a larger terminal sire breed (e.g. Simmental, Charolais, Limousin or South
Devon). The main disadvantage of this system is the need to organise a reliable
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
110
source of replacement heifers. However, if it can be managed, it is the simplest and
most effective system. The risk of introducing new diseases onto the farm, by
purchasing replacements from off-farm, has to be managed.
2. Three breed specific cross
This system uses three breeds which should all complement each other.
For
example the first two breeds (the breeding cow) can be chosen to achieve maternal
heterosis and adaptation to an environment (e.g. Hereford x Angus) whilst the third
or terminal sire breed such as Charolais or Simmental can produce the most
acceptable sale animals using growth and carcass characteristics.
For example, in a 300 cow herd:
105 of the Angus heifers, 3 year and possibly 4 year old cows (35%) are bred
to Angus bulls to generate replacement Angus heifers
75 of the Angus 4, 5 and 6 year and older cows (25%) are bred to Hereford
bulls to generate Hereford x Angus heifers
120 of the Hereford x Angus heifers and cows, and aged Angus cows (40%)
are bred to a terminal sire (Simmental) and all progeny are slaughtered.
Heifers may go to an easy calving sire (Shorthorn, Saler).
This system utilises pure-bred and crossbred heifers on the same farm. It is more
complex, requiring a large herd with at least 3 mating and calving groups.
3. Rotational crossing (sometimes referred to as criss-crossing)
In this system two, three, or more breeds of bulls are utilised in a rotational mating
system. In a two-breed rotation if Breed A cows are mated to Breed B bulls then all
heifers born to this cross are always mated to Breed A bulls (Figure 6.5). Hereford and
Angus breeds have traditionally been utilised in this method and can stabilise at around
67% of maximum heterosis.
A three breed rotational cross (Figure 6.6) has been used at Limestone Downs farm,
Port Waikato for over 13 years utilising crossbred cows comprising the Angus, Hereford
and Friesian breeds. Heifers born from the mating of one of these sires are mated to
next bull breed in the rotation for the rest of their productive lives. A fourth breed can be
introduced to a quarter of the herd (usually adult cows) as a terminal sire breed. Some
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
111
results from the Limestone Downs system are given in Table 6.9.
These results
demonstrate the lift in calf weaning weight achieved with no increase in cow liveweight.
Figure 6.5:
Two-breed rotational crossing
Figure 6.6:
Three breed rotational crossbreeding system
Table 6.9: Cow and calf weaning weights. Source: Lowe (1994).
Cow Breed
Calf weaning weight (kg)
Cow weaning Weight (kg)
Angus/Hereford
220
445
Friesian/A x H
250
410
It is worth noting that Friesian cross cows produce high calf weaning weights, but in an
intensively farmed system the feed required to restore cow liveweight lost during lactation
has to be diverted from some other enterprise or, preferably from surplus feed that is not
required by other stock classes. The opportunity cost of this diverted feed needs to be
taken into account.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
112
6.9.2
Composite breeds
The use of composite breeds where 3 to 8 breeds have been interbred to form a new breed
is a possibility.
Research from USA indicates that composite or synthetic breeds may
maintain as much heterosis as crossbreeds.
Operators of large, extensively managed
operations may also find composite breeding useful because it allows more flexibility at
mating, (i.e. fewer mating mobs) than other cross breeding systems.
Most composite breeds contain a breed ratio of 50% British breeds and 50% Continental
breeds. A four breed composite retains about 75% of the hybrid vigour of a F1 (first cross).
In New Zealand the use of composite breeds is in its infancy but some are available e.g.
Shaver Beef Blend and Stabilizer Composites from the Rissington Cattle Company.
Rissington source composite genetics from The Leachman Cattle Company in USA which
gives the Rissington Stabilizer composite (a composite of 50% British (Angus and Hereford)
and 50% European breeds (Simmental and Gelbvieh) access to huge gene pools in the
USA (e.g. the Leachman group sells over 1500 bulls per year).
6.9.3
Alternating breeds over time
With small herds using only one or two bulls, the choice of crossbreeding systems is
restricted. A normal rotational system cannot be used although buying in replacements
heifers (system one) is an option. By purchasing a different breed of bull every two or three
years, the two and three breed rotations may be closely approximated.
6.9.4
Benefits of crossbreeding
The relationship between the various mating systems, maximum heterosis retained and the
increase in weight of calf weaned per cow exposed is shown in Table 6.10.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
113
Table 6.10: Maximum heterosis expected in progeny (%) for various mating systems.
Mating system
Heterosis retained
Individual
Maternal
(%)
(%)
Straightbred A x A
Superiority over parent breeds
Weight of calf
Weaned
Cow mated
Increased
value at
(%)
(kg)
$2/kg LW
0
0
0
200
0
2 breed cross (A x B)
100
0
8.5
217
34.00
3 breed cross (A x B) x C*
100
100
23.3
246
92.00
2 breed
33
67
12.7
226
52.00
3 breed
86
86
20.0
240
80.00
4 breed
93
93
21.7
243
86.00
3 breed
67
67
15.6
230
60.00
8 breed
87
87
20.4
241
84.00
Rotational crosses
Composite
* For example (Hereford x Friesian) x Simmental
The prices noted in Table 6.10 have not included a premium for the growth potential of
crossbred cattle which in the past have resulted in premiums of $0.10-0.20/kg for
Simmental and Charolais cross cattle.
6.9.5
Disadvantages of crossbreeding
Despite all the above there are several disadvantages of crossbreeding:
•
Extra management:
Crossbreeding systems within a single farm can be
complicated because at the need to maintain crossbred and purebred cows in
separate mating groups.
•
More precise recording of breeds and breed groups is required.
•
Mating policy mistakes such as mating a large terminal sire to heifers may result
in calving difficulty problems.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
114
To maximise the benefits from crossbreeding, producers need to:
•
Identify the performance characteristics of beef breeding cows and their offspring
that will best suit their farming system.
•
Recognise that breeds differ in their performance attributes for maternal, growth
and carcass traits
•
Choose a breeding system which involves a compromise between breeding and
growth characteristics
•
Take into account their management skill levels and their ability to plan,
implement and monitor a crossbreeding program.
•
Adopt the most simple system within the constraints of crossbreeding and their
objectives.
6.10
Further reading
Anon.
2002.
Bull Selection.
A beef council publication available from Meat & Wool
New Zealand, PO Box 121, Wellington, New Zealand.
Anon.
2000.
Beef cattle recording and selection. Department of Primary Industries,
Brisbane, Queensland ISSN 0727-6273.
Baker, R.L.; Carter, A.H.; Morris, C.A.; Johnson, D.L. 1990. Evaluation of eleven cattle
breeds for crossbred beef production: Performance of progeny up to 13 months of
age. Animal Production 50: 63-70.
Baker, R L.; Morris, C A.; Johnson, D L.; Hunter, J C.; Hickey, S M. 1991. Results of
selection for yearling or 18-month weight in Angus and Hereford cattle. Livestock
Production Science 29: 277-296.
Charteris, P.L.; Garrick, D.J.
structure.
1996.
Characterisation of beef cattle breeding industry
Proceedings of the New Zealand Society of Animal Production 56:
386-389.
Lowe, K.I.
1994.
Managing the high performance beef cow herd - where to next?
Proceedings of the New Zealand Society of Animal Production 54: 315-317.
Morris, C.A.; Amyes, N. C.; Cullen, N. G.; Hickey, S. M. 2006. Carcass composition and
growth in Angus cattle genetically selected for differences in pubertal traits.
New Zealand Journal of Agricultural Research 49: 1-11.
Morris, C.A.; Baker, R.L.; Carter, A.H.; Hickey, S.M. 1990. Evaluation of eleven cattle
breeds for crossbred beef production: carcass data from males slaughtered at two
ages. Animal Production 50: 79-92.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
115
Morris, C.A.; Baker, R.L.; Hickey, S.M.; Johnson, D.L.; Cullen, N.G.; Wilson, J.A. 1993.
Evidence of genotype by environment interaction for reproductive and maternal traits
in beef cattle. Animal Production 56: 69-83.
Morris, C.A.; Baker R.L.; Hunter J.C. 1992. Correlated responses to selection for yearling
or 18-month weight in Angus and Hereford cattle. Livestock Production Science 30:
33-52.
Taylor, R.E.; Field, T.G. 1999. Beef production and management. Third Edition. Prentice
Hall, New Jersey.
Davis, G.P. 1993. Genetic Parameters for Tropical Beef Cattle for Northern Australia.
Australian Journal of Agricultural Research 44: 170-198.
Robinson, D.L.; Ferguson, D.M.; Skerritt, J.W.
1998.
Genetic Parameters for Beef
th
Tenderness, Marbling and Yield. Proc. 6 World Congress Genet. Appl. Livestock
Prod.
Profitable Farming of Beef Cows
Chapter 6: Genetics of calf production from beef cows
116
Chapter 7: Beef cattle handling and yarding
Summary
Beef cattle need to be moved into and through yards for various procedures. Factors
affecting good cattle handling include the skill of the handler, the type of animal, its previous
experiences, and the facilities and the environment. Cattle are social animals and work
best in small groups. They remember bad experiences but can learn quickly to move
through yards. With good people and good yards, little effort and no brutality should be
needed to work cattle.
The working distance is the distance at which cattle start to move away from humans or
dogs. It can be used like an accelerator, moving into the working distance will increase the
speed at which cattle move and moving out of it will slow them down. Cattle have two
movement lines (balance points); one along their backbone and one in the shoulder-neck
region. Moving to the left or right of the backbone line will encourage cattle to move in the
opposite direction. Moving behind or before the shoulder-neck line will encourage a beast to
move forward or backwards respectively.
When cattle are yarded something unpleasant almost always happens to them. They learn
that yards, races, crushes and head bails are to be avoided.
A range of measures are described to encourage cattle to move efficiently in yards.
7.1
Introduction
Beef cattle include breeding bulls, beef cows, calves, weaners, store cattle and finishers.
Dairy bulls may also be reared as beef animals. The number and class of cattle held on a
property will determine the size and quality of the facilities required and the standard of
handling skills needed. Managing beef cattle involves moving them into and through yards
for various procedures. The degree of restraint required for a particular procedure will vary
depending on stock class and the procedure being undertaken.
Profitable Farming of Beef Cows
Chapter 7: Beef cattle handling and yarding
117
7.2
Cattle handling: Moving cattle
The factors that make for good cattle handling (Figure 7.1) include the skill of the handler,
the type of animal and its previous experiences, and the facilities and the environment.
Good handling reduces stress and danger for humans and animals, saves time and effort
and makes working with cattle more enjoyable. Rough handling makes cattle more skittish
and difficult to handle in future.
Figure 7.1:
The elements of good and safe cattle handling
The behaviour of beef cattle during mustering and yarding will be influenced by breed, class
of stock, the frequency of yarding and the style of handling. Cattle that are mustered
infrequently and are generally observed from a distance will be more skittish but may move
through yards quickly.
Cows with calves may be protective of their calves.
Seriously
aggressive or wild cows or heifers should be culled as their behaviour will affect the activity
of other animals in the herd. All bulls deserve respect as a bull may become dangerous if
overexcited.
Calmness is important in handling cattle safely and effectively. Constant awareness of what
is happening, and rapid and decisive responses are also necessary.
The knowledge
required for effective cattle management is usually learned early in life, and the experience
of working with good cattle people is beneficial to all.
Cattle do not see like humans and have poorer ability to perceive distance and speed of
movement. A simple change in footing may appear threatening to a cattle beast and it may
have to put its head down to inspect the ground. Cattle tend to move towards light and do
not enter dark areas freely. They are social animals and work best in small groups. They
Profitable Farming of Beef Cows
Chapter 7: Beef cattle handling and yarding
118
remember bad experiences but can learn quickly to move through yards.
An electric
prodder should be used sparingly, and only when the animal can actually move forward. It
may be useful for moving a cattle beast into a crush or head bail. An alternative is to twist
the tail. If the tail twist is relaxed immediately the animal moves forward it learns to move
when its tail is touched or picked up even without twisting. Beef cows should be taught this
as heifers, the key is to relax the twist once the animal starts forward.
Cattle have two movement lines (balance points); one along their backbone and one in the
shoulder-neck region. Moving to the left or right of the backbone line will encourage cattle
to move in the opposite direction. Moving behind or before the shoulder-neck line will
encourage a beast to move forward or backwards respectively.
The working distance is the distance at which cattle start to move away from humans or
dogs. It varies between individual animals and is influenced by previous handling. It can be
used like an accelerator, moving into the working distance will increase the speed at which
cattle move and moving out of it will slow them down.
The level of arousal will influence the behaviour of cattle. Over-aroused cattle may break
away, go through fences or attack dogs. Keeping cattle at the right level of arousal makes
handling easy. Cattle dislike a lot of noise, and easily become over-aroused if too much
noise is used to shift them or move them through yards. Some cattle dislike motorbikes and
overreact to them. Dogs used for mustering should be kept under control, and tied up away
from yards to reduce the level of excitement of cattle. After arriving in the yards, cattle
should be given 20 minutes to settle down before being shifted into forcing pens or
beginning drafting. The entrance to yards should be wide to allow cattle to move in without
being too tightly crushed. Bulls especially dislike other bulls coming into their personal
space: this lifts their arousal level and may cause fighting.
7.3
Working in yards
Cattle learn how to move through yards. Newly purchased stock should be moved through
yards and given the opportunity to learn the way. This will facilitate easier movement by
these cattle through the yards in future. Yard design facilitates movement. Little things,
such as a change underfoot or a shadow across a gateway, can cause cattle to baulk
(Figure 7.2). When cattle are yarded something unpleasant almost always happens to
them. They learn that yards, races, crushes and head bails are to be avoided. Therefore,
Profitable Farming of Beef Cows
Chapter 7: Beef cattle handling and yarding
119
everything that can be done to encourage movement into races and head bails should be
done.
Figure 7.2:
The following is a list of reasons why cattle baulk.
•
People in the way
•
Noise – they hear shouting, clanging or bawling from the front of the race
•
Activity - they see activity at the front of the race
•
Smells that are unfamiliar or frightening
•
Dead ends – such as a loading ramp directly in front of the head bail
•
Unfamiliar yards
•
Shadows across their pathway
•
Change underfoot, such as a change of surface, drains
•
Cattle in adjacent pens standing stationary or going in opposite direction
•
Sunlight in their eyes
Drafting cattle is a basic procedure and is usually carried out through a gateway. Slow
deliberate movements, the restrained use of a piece of alkathene piping or a flag and
definite encouragement when the animal chosen is headed through the gate is required.
Eyeing the cattle to prevent movement and ceasing eye contact once the animal moves
appropriately is important during drafting.
The arousal level of cattle must be kept low and quiet animals should be drafted away from
more excited stock. It is usual to draft cows from calves as the former have experienced
drafting before. Drafting should be from small mobs and when mistakes occur the animal
should be left in the incorrect mob until the drafting is complete. Harried cattle are difficult to
draft through a gate as they tend to bunch and are reluctant to separate from the mob. It
may be better to draft them through a race.
7.4
Using forcing pens
Forcing pens are designed to funnel cattle into a race. These should be narrow enough to
allow cattle to be worked from outside the pen, preferably from a cat walk. It is best not to
work inside the forcing pen if possible. Forcing pens should never be over filled as this
prevents cattle from being directed to the entrance of the race. The material underfoot
Profitable Farming of Beef Cows
Chapter 7: Beef cattle handling and yarding
120
should be the same in the pen as in the race. Cattle may baulk at the junction of a dirt
floored pen and a concrete race.
7.5
Working in races
People should not get into races with large cattle, nor should they stick their arms or heads
into races. If working in a race with small cattle, work should start at the front of the race
and proceed backwards. The race should be packed tight to prevent stock movement and
reduce space to kick. Working from a cat walk is preferable to working from the ground as
being above the cattle offers some advantages. The cat walk and race wall height should
be sufficient to prevent a person falling into the race. Workers should not bend too low over
an animal to inject them or to place an ear tag, as cattle may lift their heads suddenly and
hit the worker in the face.
It is important to fill a race tightly if cattle are to be treated from a catwalk as this prevents
cattle moving back and forward as they are treated. Filling is done best by walking back
along the catwalk and encouraging cattle to move forward through the shoulder balance
point. An automatic shutting gate at the tail of the race assists with packing the race tightly.
Cattle move best into straight races if:
•
The conditions underfoot do not change
•
They cannot see or hear activity at the front of the race
•
They can see ahead up to light coming through the head bail
•
The sun is not in their eyes
In a squeeze crush, cattle need to be restrained at the optimum pressure, not too tight and
not too loose. Cattle remember being hurt by equipment and will baulk at entering them in
future.
Catwalks make life easier and safer Journeaux photo here
Profitable Farming of Beef Cows
Chapter 7: Beef cattle handling and yarding
121
7.6
Yard design
Most yards are square or rectangular in shape with a straight race leading off a forcing pen
up to a crush and head bail. Newer yards may have circular or semi-circular designs to
encourage animal flow. Yards should be on flat ground and be well drained. Cattle tend to
move up a slope, so if the yards are on a slope, use this to facilitate movement into forcing
pens and races. There should be no large stones or pieces of timber underfoot which may
trip up people. Bolts should be cut off flush with nuts and not stick out. Boarding should be
placed to act as a blinker to prevent cattle from seeing outside the yards.
Boarded up yards, pens and races may encourage quicker movement of cattle, as they may
head towards possible escape routes through gates and into races. In a straight race the
leading animal should be able to see right through the head bail. A visual barrier such as a
loading ramp will act to stop the lead animal two body lengths back and well away from the
head bail. This is common in yards and it makes getting cattle into the head bail difficult.
The entry gates into yards should be wide to facilitate entry. Drafting gates should be wide
enough to allow drafting by two persons without too much difficulty. Corners should be
boarded up to stop cattle piling up into a corner. Escape routes should be available and
underfoot should be dry and firm without anything to trip people up.
One wall of the forcing pen should run straight onto the race and the other should be at a 30
degree angle. The tail of the race should be straight for 2 or 3 cattle body lengths to
encourage cattle to enter. The race tail gate should have an automatic latch to make
closing easy.
The use of semicircular forcing pens and races may reduce time to move cattle by up to
50%. Semicircular races and their forcing pens are usually boarded up. This calms cattle
and prevents them seeing what is happening elsewhere. If the race is semicircular cattle
enter it thinking they are returning to where they came from. The lead animal moves
around the race because it cannot see anything else and is looking to escape. Followers
tend to chase the preceding animal as they do not want to lose sight of it.
Cattle in
semicircular races also move around people who can hit the boarding or poke a stick
through holes in the boarding to encourage movement.
The shape means that cattle
suddenly come into the crush or head bail without time or space to baulk. Loading ramps
can come off the semicircular race and not act as a barrier.
Profitable Farming of Beef Cows
Chapter 7: Beef cattle handling and yarding
122
7.7
Conclusions
The key to working cattle effectively in yards is in the behaviour of people and cattle rather
than in the design of the yards. Calm, but alert and active people will shift and treat stock
safely and quickly without difficulty.
Well handled and trained cattle respond to quiet
handling. The occasional wild animal should be culled to prevent bad behaviour spreading.
Some simple modification to yards may speed up cattle movement and reduce baulking.
With good people and good yards, little effort and no brutality should be needed to work
cattle.
The key areas to encourage cattle to move efficiently in yards are:
7.8
•
Board up the wall of the forcing pen at the entrance to the race
•
Make sure head bail opens onto open space or paddock
•
Board up the race
•
Make footing similar through forcing pen and race – remove drains and grating
•
Board up curved races
•
Use small pens so as to work smaller groups of cattle
•
Build yards to use a rise in ground to encourage cattle to move forward
•
Do not position race so that sun shines down along it during usual working hours
•
Board up corners of square yards
•
Use rubber tubing to reduce clanging of steel gates
•
Hang gates so that they open and close freely
•
Use automatic closing gates on back of race and forcing pen
Further reading
Stafford, K. J. 1997. Cattle handling skills. ACC Wellington, New Zealand.
Grandin, T. 2007. Livestock handling and transport. CABI, Wallingford, England.
Profitable Farming of Beef Cows
Chapter 7: Beef cattle handling and yarding
123
Appendix 1: Condition scoring (CS) for beef cows
Figure A1.1:
Areas to observe when Body Condition Scoring (BCS, or just CS) beef
cows. Note the focus on observing the rear half of the animal.
Profitable Farming of Beef Cows
Appendix 1: Condition scoring (CS) for beef cows
124
Table A1.1A: Description of different body condition scores (BCS) on a 1 to 5 scale.
(Refer to photos also: Figure A1.2.)
BCS
0
Thin
Condition
Description
Extremely emaciated, and on the point of death
0.5
Very extremely emaciated, with no fat detectable over spine, hips,
or ribs. Tailhead and ribs project prominently. Serious welfare
issues.
1.0
Emaciated, emaciation with no fat detectable over spine, hips, or
ribs. Tailhead and ribs project prominently. Serious welfare issues
1.5
Poor, still emaciated but tailhead and ribs are less prominent.
Spine still sharp but there is some tissue over the spine. Welfare
issues.
2.0
Thin, ribs still identifiable but not as sharp to the touch. Some fat
along the spine and over the tailhead. Efforts should be made to
improve condition
Borderline
Condition
2.5
Borderline, individual ribs no longer obvious. The spine is still
prominent but feels round rather than sharp. There is some fat
cover over the ribs and hip bones.
Good
Condition
3.0
Moderate, good overall appearance. Fat cover over the ribs feels
spongy and areas on either side of the tailhead have fat cover.
3.5
Moderate plus, firm pressure must be applied to feel the spine. A
high amount of fat is present over the ribs and around the tailhead.
4.0
Good, cow appears fleshy and carries some fat. Spongy fat cover
over the ribs and around the tailhead. Fat patches are becoming
obvious.
4.5
Fat, fleshy and over conditioned. Spine almost impossible to
palpate. Large fat deposits over ribs, around tailhead, and below
vulva. Patchy fat.
5.0
Extremely fat. Tailhead and hips buried in fat. Bone structure no
longer visible. Animal’s mobility possibly impaired, welfare issues.
Fat
Condition
Profitable Farming of Beef Cows
Appendix 1: Condition scoring (CS) for beef cows
125
Table A1.1B: Description of different condition scores (CS) on a 1 to 10 scale. (Refer to
photos also: Figure A1.2)
CS
Description
1
Short ribs prominent and sharp, absolutely no fatty tissue over spine,
hips or ribs, tail head and ribs project prominently, severe welfare
issues
2
No fat felt, welfare issues
3
Short ribs are sharp to touch and easily distinguished, animal is very
thin
4
Some fat on the pins, the backbone is bumpy, i.e. you can see the
individual backbone notches.
5
Can identify short ribs individually, feel rounded, hips and pins are
rounded, backbone is flat not bumpy
6
Can only feel the short ribs with firm pressure. Fat cover is easily felt
on tail. If cannot feel short ribs and the loin is rounded go above CS
6, if not go below CS 6.
7
Backbone can only be felt by pressing down firmly – back is flat
across loin.
8
Short ribs cannot be felt, even with firm pressure Light rounds of fat
on tail, soft to touch
9
Short ribs completely covered in fat, tail head buried in fatty tissue,
obese
10
Heavy and lumpy covering of fat over the hips, pins, backbone and
ribs, very obese
The five occasions when it may be beneficial to condition score beef cows are:
•
Weaning time - this ensures young cows (heifers) are given priority if they are in
poor condition
•
30-45 days after weaning - to see how feeding is going and adjust accordingly
•
60-90 days prior to calving - last opportunity to get things correct prior to calving
•
Calving - separate the thin cows and priority feed these
•
Mating - gives an indication of next year’s production levels
Profitable Farming of Beef Cows
Appendix 1: Condition scoring (CS) for beef cows
126
Target liveweights and CS for beef cows on three different types of land, at critical times of
the year (weaning, mid winter, pre-calving and mating) are shown in Table A1.2. The three
different cow sizes corresponding to different land could also represent different sized cows
or breeds.
Table A1.2:
*
Target seasonal liveweights and CS for various land types.
Weaning
Mid Winter
Pre calving
Mating
Hard hill country
430
380
400
410
Easy hill country
470
420
440
450
Good Conditions
550
500
520
530
Condition Score
(1 to 5 scale)
3 - 3.5
2.5*
2.5*
2.5 - 3.0
Condition score
(1 to 10 scale)
6+
5*
5*
5.5
These condition score values are somewhat negotiable, provided the cow is fit and
healthy, has good blood magnesium levels and can gain weight to reach the mating
condition score targets shown.
Profitable Farming of Beef Cows
Appendix 1: Condition scoring (CS) for beef cows
127
Figure A1.2:
Photos of Simmental cows showing various condition score values for both
0 to 5 and 1 to 10 scales.
CS 2.0 (4)
CS 2.0 (4)
CS 2.5 (5)
CS 3.0 (6)
CS 4.0 (8)
CS 4.0 (8)
Profitable Farming of Beef Cows
Appendix 1: Condition scoring (CS) for beef cows
128
Appendix 2: Nutrient composition of commonly available feeds
for cattle and sheep
DM
(%)
Feedstuff
Cr protein
(g/kg DM)
ME content
(MJ/kg DM)
Mineral content (g/kg DM)
Ca
P
Mg
Na
GREEN FEEDS
Grass/clover mixes
Spring,
leafy
14
240
11.8
6.0
4.5
1.5
1.5
Summer, leafy
20
150
10.0
8.5
4.0
2.0
2.0
dry & stalky
25
100
8.0
7.0
3.0
2.0
1.0
autumn saved
17
200
10.0
7.0
4.0
1.8
1.5
leafy
14
260
11.2
7.0
4.5
1.5
1.5
Kikuyu grass, summer
22
140
8.5
6.0
3.9
1.8
0.6
Lucerne, leafy
18
280
12.0
16.0
3.0
2.5
0.6
23
220
10.0
13.0
2.8
2.4
0.5
Maize, 1.3 - 1.6m
22
90
10.3
4.0
2.5
1.5
0.2
Oats,
leafy
18
180
12.3
6.0
3.0
1.5
4.0
Paspalum, leafy
18
180
10.5
7.5
4.0
2.5
0.6
23
100
9.3
5.6
3.0
2.5
0.4
Red clover, spring
17
280
11.5
11.0
3.5
3.0
0.8
Sorghum, Sudax (1m)
20
180
10.0
4.7
2.3
2.0
0.2
Tama ryegrass
12
240
12.0
4.0
4.0
1.5
2.5
White clover
15
280
12.2
12.0
4.0
3.0
3.0
Pasture, high quality
23
200
10.0
7.0
4.3
1.7
1.7
Pasture, poor quality
28
150
8.0
5.5
2.8
1.4
1.6
Lucerne
20
200
9.5
10.0
2.6
2.0
0.5
Maize, early dent
30
80
10.3
3.0
2.0
1.2
0.1
good quality
85
170
9.7
8.0
4.0
2.0
2.0
medium
85
110
8.5
6.0
3.5
1.9
1.7
poor
85
70
7.3
4.0
3.0
1.8
1.5
Winter,
10-20% flower
flowering
SILAGES
HAYS (pasture)
Profitable Farming of Beef Cows
Appendix 2: Nutrient composition of commonly available feeds for cattle and sheep
129
Feedstuff
DM
(%)
Cr protein
(g/kg DM)
ME content
(MJ/kg DM)
Mineral content (g/kg DM)
Ca
P
Mg
Na
STRAWS
Barley
85
40
6.5
3.0
0.8
1.7
1.1
Maize stover
85
50
7.5
6.0
1.0
4.5
0.7
Pea
85
80
7.0
16.0
1.2
-
-
Ryegrass
85
60
7.5
4.0
3.0
1.5
1.5
Carrots
12
9.9
13.2
0.4
0.4
0.2
1.0
Choumoellier
15
145
11.5
15.0
2.4
2.7
3.3
Fodder beet
18
100
11.5
1.2
1.7
-
-
Mangolds (roots)
10
100
11.5
1.5
1.8
2.0
6.0
Potatoes
24
90
12.0
0.3
2.5
1.0
1.0
Pumkin
8.4
16
12.9
0.3
0.5
0.1
0.0
Rape
17
160
12.0
15.0
4.0
0.7
0.5
Swedes, bulbs
10
120
12.4
1.3
2.0
2.0
1.0
tops
15
150
12.8
25.0
2.7
4.0
2.0
Turnips, bulbs
9
150
12.4
6.0
3.0
2.0
2.0
tops
13
180
12.8
35.0
3.4
4.0
3.0
Barley
86
110
13.0
0.6
4.4
1.8
0.3
Bran (wheat)
86
160
9.8
1.0
12.0
6.0
0.4
Linseed cake
87
300
12.0
4.4
8.0
6.0
0.7
Lucerne meal
87
200
11.0
16.0
3.0
3.0
1.5
Maize
86
80
13.6
0.03
4.2
2.0
0.03
Oats
86
130
11.5
1.1
3.9
1.4
0.1
Palm kernel extract (PKE)
90
16
11.0
0.3
0.7
0.3
0.0
Peas
87
240
13.0
1.4
4.3
1.7
0.1
Skim milk powder
94
350
13.0
12.5
10.0
1.2
6.0
Soya beans
90
500
12.9
2.7
5.5
2.6
0.1
Wheat
86
130
12.6
0.6
4.0
1.6
0.1
Brewers grain
24
230
10.0
3.0
6.0
1.0
2.0
Molasses
75
40
12.0
12.0
1.0
4.3
1.5
Urea
99
2875
-
-
-
-
-
CROPS/BYPRODUCTS
MISCELLANEOUS
Profitable Farming of Beef Cows
Appendix 2: Nutrient composition of commonly available feeds for cattle and sheep
Meat & Wool New Zealand
0800 696 328
www.meatandwoolnz.com