Daniel Fournier, agr.
Technical Services-Polygastrics Director
Eastern Region
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High quality forages are the key to successfully reducing feed
costs. This can be accomplished by harvesting and storing
high-yielding, excellent quality forages. When a crop is cut
at the right time and harvested quickly under good weather
conditions, the protein and energy levels will be at optimal
levels to support high levels of milk production. Late harvesting
will reduce the nutrient content, the digestibility and the intake
of that forage. There are many factors that influence the quality
of forages, but the most important factor is the maturity of the
plant. Young, pre-bloom forages are generally higher in protein
and energy than older mature material that has bloomed.
As the crop matures the plants quality will decline quickly.
So, when and how do you determine when it is time to cut?
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in the late bud to early bloom stage. An easy way to predict heading and
blossoming is to measure accumulated degree days. There is a strong
relationship between degree days and quality. The table below shows
forage quality in relation to degree days. According to this 3 year study,
the maximum yield and quality for grasses is reached at 300 degree
days. For legumes, this potential is reached at 400 degree days.
Experience, knowledge and various tools allow you to make a very good
educated guess when to harvest by simply estimating the stage of
maturity of your crop. One method is you can calculate the growing degree
days to help you in the decision making process. Grass forages should
be cut at the beginning of the heading stage and legumes should be cut
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DEGREE
DAYS
ALFALFA
TIMOTHY GRASS
MIX
DEGREE
DAYS
ALFALFA
TIMOTHY GRASS
MIX
C.P. %
ADF %
C.P. %
ADF %
C.P. %
ADF %
400
20.6
29.7
11.1
34.7
15.6
32.4
23.7
425
20.1
30.5
10.7
35.4
15.2
33.1
25.5
450
19.7
31.2
10.3
36.1
14.7
33.8
475
19.3
31.9
10.0
36.7
14.4
34.5
500
18.9
32.5
9.7
37.3
14.1
35.1
525
18.6
33.1
9.4
37.8
13.8
35.6
30.6
550
18.3
33.6
9.2
38.3
13.5
36.1
31.5
575
18.1
34.1
9.0
38.7
13.3
36.6
C.P. %
ADF %
C.P. %
ADF %
C.P. %
ADF %
200
31.8
18.9
22.4
24.1
26.7
21.7
225
28.8
20.9
19.2
26.1
23.7
250
26.7
22.6
17.0
27.9
21.6
275
25.1
24.2
15.3
29.4
19.9
27.0
300
23.8
25.5
14.1
30.7
18.7
28.3
325
22.8
26.7
13.1
31.9
17.7
29.5
350
21.9
27.8
12.3
32.9
16.9
375
21.2
28.8
11.7
33.8
16.2
Source: Perron agr., M. and Boisclair agr., M. May 1993.
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Here are some recommended “Best management practices” that should
be considered to harvest high quality forages :
• Mow the hay crop early in the day to allow a full day of drying
to reduce losses from respiration.
• Form a wide swath to increase the drying rate.
• Chop at correct moisture for your type of silo to optimize preservation.
• Fill rapidly to reduce the growth of molds and harmful bugs.
• Consider the use of preservatives to reduce heating in storage
and preserve the quality of your forage.
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The major contributions of forages to the ration are fiber and carbohydrates, which are an excellent source of energy. The energy to the cow
comes from her ability to ferment these forages in the rumen. With
higher forage digestibility the cow will generate more energy from the
forages. But how do we know what is more digestible to the animal?
Before looking at digestibility, we have to look at what is fermented.
It is important to know the “true fiber” content of the forage and diet.
The “true fiber” will be fermented in the rumen and this will provide
a large part of the cows energy requirements.
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Since forages account for over 50% of the ration, it is critical to evaluate
the fiber contribution correctly. To achieve the most accurate determination of the true fiber content of forage and its digestibility, Landmark
Feeds introduced two new analyses called Potential Digestibility (PD) and
Insoluble Fiber (IF). Insoluble Fiber provides a more precise measure
of the insoluble cell wall (cellulose, hemicellulose and lignin) of the
forages, while Potential Digestibility estimates how much of the forage
can be digested. Now that we have the true fiber content and the
digestibility of your forages we can predict how much energy
(carbohydrates) these forages will provide to the cow.
NEWTON is the only program on the market that can use this information
and maximize the use of your forages. NEWTON will calculate the amount
of fermentation going on in the rumen and with this information adjust
the level of concentrates needed to optimize milk production. In the figure
below, you can see the variation in Potential Digestibility of corn silage.
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30
% samples in each category
Harvesting at these stages will provide you a NDF value of 40% for
legumes, 50% for grasses and 45% for mixes. It is better to start a little
earlier to make sure you capture as much quality as possible before
the end of your harvesting period. Remember, plant quality declines
significantly as the plant matures. Plant measures taken every two
to three days have shown that the plant cell wall content increases,
digestible carbohydrate decreases, and lignin accumulates.
25
20
15
10
5
0
60
64
68
72
76
80
Potential Digestibility in %
84
88
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Most of the samples are in the high (> 75%) range, but you can see that
25% of them are in the low range. Samples from the high end will supply
more energy to the cow and this will reduce the amount of concentrates
you will need to supply to your cow. More dollars can be saved if your
forages are in the upper end of the scale.
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Let’s take a look at different digestibility values and see what the
impact is on ration costs.
In the following table, all the rations where formulated with the same
forages. The only difference was the PD value of the haylage. As we
balance the ration with a high PD versus a low value, your feeding
cost goes up. In this scenario, the cost difference was as much as
36 cents/cow/day. This is more than $6,000 per year for a 50 cow herd.
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PD 80
PD 75
PD 70
PD 65
28.53
26.29
23.0
21.6
HAYL
10
10
10
10
CORN SIL.
1
1
1
1
DRY HAY
7.49
8.23
9.29
9.64
CORN
3.43
3.50
3.63
3.80
SUPPL.
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+0.25
+0.36
COST $/C/D
Another way to look at this is to determine a price for the haylage based
on quality. In this scenario, the potential cost difference between
the high and low PD haylage is $49 per metric tonne. In otherwords,
the 80 PD hayalge is worth $49/MT more than the 65 PD haylage.
Forage digestibility does play an important role in your operation
and bottom-line.
We all know forages are important to the cows and to the dairy operation.
Harvesting them on time and preserving them in the best possible
way is what you try to do every year. If Mother Nature cooperates,
and I hope she will this year, it makes harvesting easier. With a little
more information on Digestibility (PD) and its impact on costs, you
are now in a better position to plan your next harvest. Keep in mind
that cows at different stages of lactation have different needs. If you
happen to harvest forages with a lower PD value, there will always
be a place to use this feed wisely.
Landmark Feeds and its network of sales representative can help you
make the best choices for your operation. Do not hesitate to contact them
for further discussion. Have a nice summer!
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