Report from the working group on conformation traits
A National System for
Recording Conformation Traits
SUMMARY
A recording program for conformation traits is proposed based on the information
available in the literature and the practical needs of the Canadian Swine Industry.
A brief review is provided on the following aspects:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
The need for recording conformation traits
Importance to producers
Systems used in other countries
− Traits measured
− Number of classes
Criteria for choice of suitable measures
Heritability estimates
Genetic correlations with production traits and longevity
− Correlations with growth
− Correlations with longevity
Economic values
Accuracy of the measurements
Concluding remarks
Proposed system of scoring
Time of recording
Steps for implementation
Next steps
The proposed system includes scores for fore legs, hind legs and underlines. The fore legs
and hind legs are scored from the distal end and sides as well as for the condition of the
pasterns into five categories each. Scoring of underlines is based on the number of
functional teats.
Necessary steps for implementation of the scoring system and steps for use of the
information for genetic evaluation are also discussed.
A National System for Recording Conformation Traits: March 2001
Report from the working group on conformation traits
A National System for
Recording Conformation Traits
1.
Introduction: The need for recording conformation traits
-
Breeding animals must be physically sound and structurally correct to carry out
their normal functions. Animals that cannot maintain minimum levels of physical
soundness need to be culled earlier from the herd resulting in economic losses.
-
In general, the relevance of conformation traits in pigs depends mainly on their
relationship with involuntary culling and on their productive value for other
economically important traits. In commercial herds the conformation of sows is
mainly used to predict the risk of involuntary culling. Reducing involuntary
culling of sows has several advantages such as reduction in annual cost of
replacement, increase of average number of piglets per litter because of
decreasing number of first parity sows, reduction in number of non-reproductive
days and increased opportunity for selection on other traits.
-
Independent culling for conformation traits has been done for many years. This is
mainly based on a subjective phenotypic evaluation and a prediction about the
future productive life of the individual or its female progeny. However, in many
cases this phenotypic evaluation is overemphasized leading to a reduction in
selection intensity for index traits. In many herds about 80-90% top indexing
boars and gilts are culled on the basis of their conformation. This has resulted in
reducing genetic progress by more than half in many herds, and has a tremendous
effect on the overall rate of genetic improvement and economic benefits to
breeders and producers.
-
Very often the basis for genetic improvement of specific traits is their economic
value or their relationship with traits of economic importance. Conformation traits
seem to have a moderate economic value compared to index traits but they have a
significant impact on the economic benefits from index traits. Therefore, if proper
attention is not given to the selection and improvement of conformation traits,
independent culling for conformation may undermine the efforts to improve other
traits that are economically more important.
-
Despite a long history of selection or rather independent culling for conformation,
many breeders have observed limited improvement over the past years. Rather the
situation has become worse. It is argued that one of the reason for this is the
negative correlation with the index traits, especially growth rate. As the pigs
become leaner and fast growing they seem to have more feet and leg problems
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A National System for Recording Conformation Traits: March 2001
due to disproportionate growth of the bones and tendons. This may be true to
some extent. Some of these negative correlations are documented in the literature.
-
However, this also indicates that phenotypic selection for conformation over the
past years has not resulted into progress in conformation traits sufficient to
overcome this negative effect of faster growth rate. If proper attention is given to
selection for conformation traits, considering the negative correlation with growth
traits, it should be possible to make reasonably more progress in both growth and
conformation traits.
-
One of the reasons for the lack of genetic progress in conformation traits is the
lack of a proper system for recording and genetic evaluation. Systematic selection
for conformation traits has been carried out for several years in many European
countries, however, in Canada the first milestone of the selection process for
conformation, a national system for recording it, is still missing.
-
This study addresses the issue of recording conformation traits. The use of this
information for genetic evaluations and selection will be discussed later when a
recording system is established and some data are available to develop a genetic
evaluation system.
2.
Importance to producers
-
The first question is, is it really important to the producers? This question was
asked to a random sample of 500 producers who bought gilts from the Danish
Breeding System. The survey was part of an investigation to study the
significance of selection for conformation and its effect on longevity of sows
(Andersen and Hansen, 1996). Following are the percentages of responses of
producers based upon their rating of the significance of three measures of
conformation.
Length
Width
Legs
Very important
9
6
90
Important
38
40
10
Not very important
49
50
0
Not at all
4
4
0
-
The above survey included only linear measurements of length and width and the
condition of the legs. However, it clearly shows that legs are more important to
producers than length and width.
-
In a different study in Sweden, different reasons for culling of sows were recorded
on 3990 sows in commercial systems. The study revealed that about 30% animals
were culled for unsatisfactory production results (litter size), 23% for fertility
problems and 11% for leg weakness.
3
A National System for Recording Conformation Traits: March 2001
-
A more detailed investigation was done where the reasons for culling were
prioritized in terms of main reason, secondary reason and so on. The following
were the main reasons for culling in a smaller group of 908 sows.
Reason for culling
Fore legs
Rear legs
Claws
Udder
Productivity (litter size)
Fertility problems
Disease
Other reasons
Total
Number
14
131
17
65
198
278
50
155
908
%
2
14
2
7
22
31
6
17
100
-
This study shows that about 25% sows are culled due to poor conformation, which is
the largest factor after fertility problems and almost as significant as litter size.
-
Among the conformation traits, rear legs and underlines were the most important after
fore legs and claws.
3. Systems used in other countries
Traits measured
A number of scoring systems have been proposed and used in other countries,
especially in Europe. These scoring systems are different in terms of the traits
recorded, number of categories per trait and differentiation between classes.
Following is a summary of the published systems.
Traits
Scale
Country
Year of
beginning
1982
Source
Forelegs, hind legs, gait
pattern, back and loin,
hams, claws, underlines,
etc.
(21 conformation traits)
(Appendix 1 and 2)
Fore legs, hind legs,
shoulder, back and loin,
hams, stature, underlines
(14 exterior traits)
Front legs, hind legs,
locomotion
Fore legs, hind legs,
locomotion, stance,
back, underlines
(Appendix 3)
Fore legs, hind legs,
back, overall approval
Nine categories with the
possibility of scoring
intermediate values
Sweden
Three categories
(1-2-3 system)
The
Netherlands
1982
Koning
(1996)
Nine categories
Sweden
1993
Three main categories
with options to record
slightly defect or
severely defect
Five points for
approval, three for other
traits
Norway
1993
Lundeheim
(1996)
Grindflek
and Sehested
(1996)
Denmark
1995
Van
Steenbergen,
(1989)
Andersen
and Hansen
(1996)
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A National System for Recording Conformation Traits: March 2001
-
In the US, the NSIF guidelines (1996) suggest scoring of fore legs and hind legs in 5
categories each. Thereafter, front and rear scores are summed and the following
scoring format is used:
1. Unacceptable (1-3 points). Severe structural problems that restrict the animal's
ability to breed.
2. Good (4-7 points). Animals with slight structural and/or movement problems.
3. Excellent (8-10 points). No obvious structural or movement problems. (Includes
even toe size, adequate length of stride, adequate flexion of hock and pastern
cushion, trueness and freeness of movement.)
-
The scoring format for the underline soundness is as follows (NSIF, 1996)
1. Unacceptable (1-3 points). Fewer than six functional nipples on each side or one
or more inverted nipples or poor spacing and prominence.
2. Good (4-7 points). Six or more functional nipples on each side with adequate
spacing and prominence.
3. Excellent (8-10 points). Six or more functional nipples on each side, well-spaced
and well-developed with no pin or blind nipples.
-
A large number of traits were recorded in most of these systems (as much as 21
traits). The most common traits were fore legs, hind legs, and underlines. Some
programs have also used locomotion.
-
As the number of traits increases the scoring method becomes more complex and
time consuming and the genetic progress in each individual trait decreases. It is
important to record the minimum number of traits that are the most important, at least
when the national system for conformation scoring is first established.
Number of classes
-
The scale of recording is very important. A classification in three categories (threepoint scale) has an advantage that the scoring is clear and easy e.g. the fore leg can be
classified either as buckled, sickled or normal and pasterns can be classified as high,
low or normal. However, this classification does not allow much differentiation (e.g.
if the fore leg is slightly buckled compared to severely buckled). The larger problem
is the difficulty in the identification of genetic variability. Hence, a classification in
three categories is not very suitable for genetic evaluation. On the other hand, if there
are a large number of categories, it is difficult to differentiate individuals between
adjacent classes and ultimately few classes end up being used. In the study by Van
Steenberg (1990) there were 9 main categories with the option to record intermediate
categories. Thus there were 17 possible classes. However, intermediate classes were
used less than the classes with whole numbers resulting in the use of 9 main
categories out of the total of 17 (Fig.1).
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A National System for Recording Conformation Traits: March 2001
20
18
16
Percentage
14
12
10
8
6
4
2
0
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 7 7.5 8 8.5 9
Category
Figure 1: Overall distribution of exterior scores into different categories
(source: Van Steenbergen, 1990)
-
This was a scientific study where the distribution in nine classes appears to be fairly
normal. However, under field conditions, even nine categories may not be used
properly due to the difficulty in differentiation between adjacent classes.
-
A five point scale is probably best in practice and also for genetic evaluations.
4.
Criteria for selecting suitable measures
In a systematic approach for genetic improvement, the choice of conformation traits
should be based on the following criteria:
−
−
−
−
5.
-
Heritability estimates
Economic value of the trait
Correlation with other economically important traits
Accuracy of measurements
Heritability estimates
Genetic parameters for conformation traits are not so common in the literature as
those for growth and production traits. However, some of the studies have been very
extensive in terms of the number of traits recorded, the number of classes within each
trait and the number of records used. Estimates reported in some studies are given by
Larochelle (1999) (Appendix 4). Following is a summary of the heritability estimates
for important conformation traits.
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A National System for Recording Conformation Traits: March 2001
Trait
Range
Average
Fore legs
Fore legs front view
Fore leg bone
Fore leg pasterns
Fore leg claws
.04
.06
.06
.31
.04
- .32
- .47
- .47
- .48
- .21
.18
. 27
.27
.40
.13
Hind legs
Hind legs rear view
Hind leg hock
Hind leg pasterns
Hind leg claws
.04
.06
.01
.07
.09
- .21
- .47
- .23
- .30
- .13
.13
. 27
.12
.19
.16
Back
.15 - .22
.19
Locomotion
.08 - .13
.11
-
Here, the averages for individual traits should be interpreted with caution because the
estimates are based on different scoring and production systems. For example, foreleg
bones in the study by Grindflek and Sehested (1996) in Norway are scored on a three
point scale and include males only while those by Van Steenbergen (1990) are scored
in Sweden on a nine point (or 17 point) scale and include both sexes.
-
Among the feet and leg traits, pasterns seem to have higher heritability. For most
other traits the heritability is around 15%. Locomotion has a lower heritability
probably because of inaccuracy of recording.
Total number of teats
− Most studies refer to total number of teats just after birth. The heritability estimates
range from 0.7 to 0.42 (Allen et. Al. 1959; Enfileld and Rempel 1961; Skjervold
1963; Pumfrey et. al. 1980; Clayton et al. 1981). Generally, teat number is considered
to be moderately heritable with a heritability of about 0.3.
− In a Canadian investigation, McKay and Rahnefeld (1990) have reported the
following estimates for Landrace, Yorkshire and Hampshire breeds.
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A National System for Recording Conformation Traits: March 2001
Breed
1962-1974
Landrace
Yorkshire
1982-1988
Landrace
Yorkshire
Hampshire
Number of pigs
Total number of teats
Haritability
5351
4711
14.1 ± .2
13.8 ± .2
.23 ± .02
.32 ± .02
1083
3803
2134
14.4 ± .3
13.5 ± .2
12.7 ± .3
.39 ± .05
.44 ± .02
.45 ± .03
− The estimates in the later part of the above study might be inflated due to an influx of
boars as suggested by the authors.
Number of functional teats
− The number of functional teats is usually measured just after farrowing as the number
of teats that deliver the milk. At earlier ages, the number of functional teats is the
number of teats excluding inverted or deformed teats where the teat canal is not
visible or apparently dysfunctional. The number of functional teats is also affected by
non-genetic factors from birth to furrowing such as teat injuries. Therefore, it is
expected to have lower heritability than the total number of teats at birth. Following
estimates of heritability were observed by Ligonesche et al. (1995) for total number
of teats and number of functional teats
Total number of teats
Number of functional teats
Maternal line
0.25 ± 0.01
0.21 ± 0.01
Paternal line
0.25 ± 0.01
0.15 ± 0.01
Inverted teats
− If the nipple fails to protrude from the surface of the udder the teat considered to be
inverted teat. The teat canal is in-wards, thus these teats are usually considered to be
non functional. However, a recent study in France (Labroue et. al., 2001) has revealed
that almost all of the inverted teats, become functional and give milk at the time of
lactation. Therefore the inverted teats should be considered as functional teats.
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A National System for Recording Conformation Traits: March 2001
6.
Genetic correlations with production traits and longevity
Correlation with production traits
-
Genetic correlations with production traits have been evaluated in a long-term study
in Holland as a part of a Ph.D. dissertation (Van Steenbergen, 1990). These estimates
are probably the most reliable because of the large number of observations and the
number of classes used. The estimates for traits included in the current index are
given below.
Trait
Heritability
(%)
Genetic correlation (%)
Average Backfat
Feed
daily
conversion
gain
Fore legs
Front view
Side view
Pasterns
Hind legs
Rear view
Side view
Pasterns
6
6
31
6
11
44
10
8
14
21
23
-15
22
23
30
-29
8
-13
4
-16
6
71
-8
3
Claws (Ratio)
Locomotion
9
13
3
-35
-25
26
-21
23
-
The correlations are reasonably high suggesting that selection on the index traits can
significantly affect conformation and vice versa. However, the magnitude and
directions of these correlations should be interpreted in relation to the scales of the
measurements. The low genetic correlations may also indicate strong nonlinear
relationships. Nonlinear relationships are especially possible because both high scores
and low scores are undesirable, for most of these traits. A positive correlation does
not necessarily mean an improvement in the production trait with an improvement in
conformation. For example, the correlation between fore leg pasterns and average
daily gain is 44%. This means a change in fore leg pasterns from a steep angle (score
0) to a low angle (score 9) is associated with an increase in growth rate. However, a
good conformation would be the normal angle (score 4.5). Hence, if the population
mean is below 4.5, improvement in conformation is associated with an increase in
growth rate. However, if the population mean is above 4.5 an improvement in
conformation is associated with a decrease in growth rate.
-
It is also interesting to note that the correlations with fore legs are positive while
some of the correlations with hind legs are sometimes negative. For example, there is
9
A National System for Recording Conformation Traits: March 2001
a negative correlation between rear view of hind legs and average daily gain
indicating that a change from O shape to X shape in the rear legs is associated with a
reduction in the growth rate. However, the same change in shape of fore legs is
associated with an increase in growth rate.
-
Therefore, the sign of the correlation and the population mean for the leg traits
together determine if selection for production traits is associated with better
conformation or vice versa. This situation makes it rather difficult to draw meaningful
conclusions based on these genetic correlations.
-
However, there is evidence of negative phenotypic correlation between good
conformation and faster growth rate based on the frequencies of the conformation
traits in fast and slow growing animals. Grindflek and Sehested (1996) found high
frequencies of weak fore leg and hind leg pasterns, uneven and small/narrow hind leg
claws, X-shaped fore and hind legs, dipped back and bad locomotion in fast growing
animals. In general, faster growth rate from 25 to 100 kg is associated with poor
conformation.
Correlation with longevity
-
Van Steenbergen (1990) conducted a detailed investigation on the relationship
between exterior traits and longevity. Over a two-year period, over 5000 gilts and
sows from different strains (Landrace, Yorkshire, Duroc and their crosses) were
judged for 20 exterior traits at 24 commercial multiplier herds. Farms were visited
monthly by an inspector who judged all gilts of approximately 7-9 months of age and
all sows from weaning till 40 days post weaning. Sows culled for leg weakness
before the fourth parity were longer and broader at the gilt stage, had less straight rear
legs and more tubercles at the rear legs, walked slower and twisted more with hind
quarters than animals that had produced at least four litters.
-
This investigation, however, did not produce any estimates of genetic correlations
with longevity.
-
Research results from a similar study suggest that longevity is strongly influenced by
exterior traits (Grindflek and Sehested, 1996). Poor locomotion and straight pasterns
lead to decreased longevity. However, contrary to the common belief in Canada, they
found that weak pasterns have a positive effect on longevity
-
According to these studies, length, width, hock joints, pasterns and locomotion are
important conformation traits with significant effects on longevity.
10
A National System for Recording Conformation Traits: March 2001
7.
-
Economic values
There is a scarcity of information about the direct economic value of conformation
traits in the published literature. In most cases, the economic values are estimated
based on relationships between individual conformation traits and longevity. Similar
procedures are followed in other livestock species. Therefore, it can be assumed that
the traits with the highest economic values are those that have the highest effect on
longevity, as described above.
8. Accuracy of measurements
-
Among the important traits of conformation that are related to growth and longevity,
the traits of fore legs and hind legs can be recorded clearly and easily at the time of
probing.
-
The average estimated time for recording fore and hind legs is about 30 seconds/pig.
-
However, locomotion is more difficult to measure accurately. It requires a calm
animal walking an even surface for some time. Therefore, it is more time consuming
and difficult to record
-
Locomotion may be replaced by scores for fore and hind legs that can be recorded
more easily and accurately
-
Grindflek and Sehested (1996) observed that sows with poor locomotion had 21%
less chance to be used after 4th parity than average sows. Standing under, straight fore
and hind leg pasterns, and sickled hock gave the highest probability of poor
locomotion. The chances of good locomotion are reduced by 39% due to the standing
under condition of hind legs, 30% due to straight fore leg pasterns, 19% due to
sickled hock and 15% due to straight hind leg pasterns.
-
These component traits of locomotion can be recorded at the time of probing in the
barns. In many studies locomotion was recorded in just two categories (good or bad),
which does not allow proper evaluation and use of genetic variability. That is one of
the reasons for the low heritability estimates reported in these studies. The use of fore
and hind leg traits can also be useful for the selection and improvement of locomotion
and longevity.
11
A National System for Recording Conformation Traits: March 2001
9.
Concluding remarks
Based on the above discussion, the following conclusions can be drawn:
-
-
The most important conformation traits are fore and hind legs, locomotion and
underlines
Among them locomotion is one of the most important factor determining
longevity
However, locomotion is difficult to record and promises less chances of genetic
improvement due to its low heritability (0.08 to 0.13)
Locomotion is mainly affected by the condition of fore and hind legs
Fore and hind legs are used in almost every system of conformation recording in
Europe, US and Canada. They might be better accepted by the breeders and
technicians than locomotion.
The conformation of legs can be recorded as front view (or rear view), side view,
pasterns and claws.
Among these, front view and rear view, side view and pasterns have a higher
effect on locomotion than claws.
Claws have lower heritability (.04 -.21) and they have not been found to affect
either locomotion or longevity significantly.
Claws can be safely excluded from the scoring system to reduce the number of
conformation traits
It is generally believed that sows must have functional teats to rear pigs. The role
and heritability of spacing, prominence, location, etc., of teats in production has
not been defined clearly by research. But, because these traits and especially the
number of functional teats may have a direct influence on production they should
be considered as part of a scoring system for conformation.
12
A National System for Recording Conformation Traits: March 2001
10.
Proposed system of scoring
Based on the above discussion, the system of recording of conformation traits should
include the following traits:
1. Forelegs
Front view
Side view
Pasterns
(scores 1.0 - 5.0)
(scores 1.0 - 5.0)
(scores 1.0- 5.0)
2. Hind legs
Rear view
Side view
Pasterns
(scores 1.0 - 5.0)
(scores 1.0 - 5.0)
(scores 1.0 - 5.0)
3. Number of functional teats
The information given in Figure 2 may be used as a guide for scoring fore and hind legs.
Scoring of fractional number between the categories
It is very important to note that one can assign a fractional number between the
categories. Scores with fractional numbers such as 3.2 or 3.7 are perfectly valid scores.
There is no need to round them up to the closet whole numbers. For example, if a pig has
slightly sickled fore legs and it is more likely to get a score of 3 rather than a score of 4
the score should be 3.1 or 3.2 or 3.4 depending upon the angle of the wrist. One should
not round up the actual score and assign it the score of 3.0. An easier way to judge the
exact value of a fractional score is to assign a value relative to other pigs in the same
management group e.g. relative to a pig that has a perfect score of 3 or a perfect score
of 4.
The scoring of intermediate numbers will be very useful to identify small differences
between animals, identify the underlying variation and do a better job on selection.
13
A National System for Recording Conformation Traits: March 2001
Figure 2: Proposed system for scoring fore and hind legs
A National System for Recording Conformation Traits: March 2001
Number of functional teats:
Functional teats are those from which milk could be expressed at farrowing. The
number of functional teats can be counted at weaning as total number of teats on
both sides of the udder excluding blind and rudimentary. Inverted teats should not
be excluded since they become functional and give milk at the time of lactation.
Following figure can be used as guideline:
1, 2 and 3 are functional teats
4 and 5 are non-functional teats
11.
Time of recording
− All these traits should be recorded on both boars and gilts at the time of probing
and the information should be sent along with the probe records.
− The number of functional teats can be recorded at the time of weaning or later
until the time of probing and the records should be sent early on (pre-listing of
pigs) or with the probe records depending upon what is possible for each regional
centre
12. Steps for implementation
− The recording can be done either by breeders or by technicians. In either case, it is
very important to ensure the accuracy and credibility of the system. This will
require an objective accreditation system just like for backfat and age and can be
done with the following steps;
− At first, the standards of recording should be tested by technicians in the
regional centres and modified if necessary;
− Then the scoring system should be used at the national and regional standard
sessions for training the technicians.
− The trained technicians can then either provide training to interested breeders
or do the recording themselves, depending on what each regional centre feels
is best.
− If breeders do it, there should be monitoring and accreditation in the same way
as we do for owner sampler records of backfat and age. Scores from
technicians or breeders to be accredited could be compared statistically to
those of a group of reference technicians.
A National System for Recording Conformation Traits: March 2001
− The regional centres can decide what to charge for the recording of conformation
traits, if the technicians do it.
− We could also start training some interested breeders. The records will be very
useful for developing genetic evaluations.
Recording number of teats
− The number of functional teats can be recorded at the time of weaning or later
until the time of probing
− The records should be sent early on (pre-listing of pigs) or with the probe records
depending upon what is possible for each regional centre
− This information can be recorded by breeders or by the technicians (need to
produce extension material and do some training)
− The information should be recorded on all pigs, including pigs that will not be
probed, as it will be useful for identifying sires who have a high percentage of
progeny that are culled because they have fewer functional teats.
Reports to breeders
− It is important to provide reports to participating breeders during the trial period
(pilot evaluation).
− The report could contain conformation scores (possibly adjusted for age) and
EBVs.
− One of these reports could show phenotypic averages for the herd along with
regional and national averages. This will help breeders compare their herd with
other herds on the program and make necessary changes to their management or
genetics.
− The EBVs for conformation traits could be reported on the same scale as actual
conformation scores after adding a mean to the EBVs (same as goat conformation
system). For example, instead of zero being the average, the average could be 3 if
the animals are scored from 1 to 5. EBVs would then range from 2.5 to 3.5 for
most animals. This reduces the chances of independent culling on conformation
traits and is ultimately useful for genetic improvement in conformation as well as
production traits.
13. Next steps
Genetic evaluation and selection
The implementation of a genetic evaluation system of conformation would require the
following steps, which would be addressed in the second part of the IRAP project once
feedback and sufficient data from the proposed scoring system are available.
− Standardization of conformation scores based on variances within contemporary
groups
− Single trait (or multiple trait) evaluation for conformation scores
17
−
−
−
−
−
Computation of economic values
Selection index based on conformation scores
Reporting
Extension article to make best use of the information
Monitoring genetic progress and revaluation if necessary
There are several options for the computation of EBVs. For example:
1. Single trait EBVs for the 7 traits and one index value for all traits based on their
relationship with longevity
2. A phenotypic combined score based on all the traits and computation of one EBV for
fore and hind legs and one for the underlines
Option 1:
- The reporting of EBVs for many conformation traits may lead to too much selection
emphasis on one or two traits and thereby reduce genetic progress. This can be even
worse if it results into reduced selection intensity for production traits. One of the
options is not to publish the EBVs but instead publish an index value based on the
EBVs for individual conformation scores. This index will take into account the
genetic correlation between the individual traits and longevity. This value can then be
included in the combined index with other production traits.
-
This approach also provides an opportunity to monitor the genetic progress in each of
the conformation scores and to change their economic values according the progress
achieved after a few years and according to future needs. For example, if it is
observed after a few years of selection that sufficient genetic progress has been made
for fore legs, their economic values can be reduced.
-
Another advantage is the possibility to customize selection for specific conformation
traits according to the requirements of individual herds. For example, if a herd is
above average for fore leg scores but has a severe problem with hind legs, the
economic values of hind leg scores can be given a relatively higher weight for faster
genetic improvement without compromising progress in production traits.
Option 2:
- A phenotypic index based on conformation scores for feet and legs can be computed
through a decision table accounting for the relationships between fore and hind legs.
For example, if both fore and hind legs are O-shaped it is not so bad as O-shaped fore
legs and X- shaped hind legs.
-
This approach provides one EBV for the whole complex of conformation scores and
reduces the chances of excessive weight on individual conformation scores.
18
-
However, this can become complicated and a consensus from breeders and geneticists
may be difficult to achieve. Another significant problem is the difficulty in predicting
response to selection in the component traits with this approach.
Recommendations:
-
-
-
EBVs for individual traits and a combined index (option 1) could seem to be the most
logical, but it is rather too early to make a definitive conclusion.
There are more than these two options. For example, other systems could also be used
such as sum of conformation scores suggested by NSIF or other similar methods used
in Scandinavian countries.
Each of these options has its own merits and drawbacks. A number of issues are
involved such as the effect on the genetic progress in conformation traits, the effect
on other traits, the accuracy of the evaluations, the flexibility for further
improvements etc.
These issues will be addressed during the next phase of the IRAP project.
19
14. References
Allen, A. D., Tribble, L.F. and Lasley, J. F. (1959) Inheritance of teat nipples numbers in
swine and relationship to performance. Mo. Agric. Exp. Sta. Bul. 694. 16
pp.
Andersen, S. and Hensen, U. G. (1996) Selection for conformation and longevity in
Danish breeding systems. Proceedings of NJF-Seminar no. 265, Denmark.
27-28 March 1996: 72-76
Clayton, G. A., Powell, J.C. and Hiley, P. G. (1981) Inheritance of teat number and teat
inversion in pigs. Anim. Prod. 33: 299-304
Dyck, G. W., Swierstra, E. E., McKay, R. M. and Mount, K.(1987) Effect of location of
the teat suckled, breed and parity on piglet growth. Can. J. Anim. Sci.
67:929-939.
Enfield, F. D. and Rempel, W. E. (1961) Inheritance of teat number and relationship of
teat number to various maternal traits in swine. J. Anim. Sci. 20:876-879
Grindflek, E. and Sehested, E. (1996) Conformation and longevity in Norwegian pigs.
Proceedings of NJF-Seminar no. 265, Denmark. 27-28 March 1996: 77-83
Koning, G. (1996) Selection in breeding programs against leg problems. Proceedings of
NJF-Seminar no. 265, Denmark. 27-28 March 1996: 85-87
Labroue, F.; Caugant, A.; Ligonesche, B. and Gaudré, D. (2001) Evolution of “abnormal”
teats in gilts during growth and first lactation. Journées Rech. Porcine en
France.
Larochelle, M. (1999) Selection for conformation traits, Review of literature. CDPQ.
Lundeheim, N. (1996) Conformation scoring in the Swedish pig progeny testing scheme.
Proceedings of NJF-Seminar no. 265, Denmark. 27-28 March 1996: 70-71
McKay, R. M. and Rahnefeld, G. W. (1990) Heritability of teat number in swine. Can. J.
Anim. Sci. 70 : 425-430
National Swine Improvement Federation (1996) Guidelines for uniform swine
improvement programs.
Pumfrey, R. A., Johnson, R. K., Cunningham, P. J. and Zimmerman, D. R. (1980)
Inheritance of teat number and its relationship to maternal traits in swine.
J. Anim. Sci. 50: 1057-1060
Skjerovold, H. (1963) Inheritance of teat number in swine and the relationship to
performance 13: 323-333
Van Steenbergen, E.J. (1989) Description and evaluation of a linear scoring system for
exterior traits in pigs. Livest. Prod. Sci. 23:163-181
Van Steenbergen, E.J., Kanis, E. and Van der Steen, H.A.M.(1990) Genetic parameters of
fattening performance in exterior traits of boars tested in central stations.
Livest. Prod. Sci. 24:65-82
Van Steenbergen, E.J., Kanis, E. Koops, W. J. and Van der Steen, H.A.M.(1990) Exterior
in sows: 1. Effect of parity number and association with reasons for
disposal. Livest. Prod. Sci.
20
Appendix 1
Conformation traits and their classifications used in Sweden
(Source: Van Steenbergen,1989)
21
Appendix 2
Drawings to illustrate classification of 8 conformation traits used in Sweden
(Source: Van Steenbergen,1989)
(6) Width of hams, (7) front view fore legs, (8) side view fore legs, (9) side view fore
legs (10) rear view rear legs (11) side view rear legs, (12) side view hock joint (13) side
view pastern real legs.
22
Appendix 3
Conformation traits and their classifications used in Sweden
(Source: Grindflek and Sehested, 1996)
23
Appendix 4
Summary of heritability estimates
(Source: Larochelle,1999)
Van
Steenbergen
et. al.(1990)
Koning (1996)
Source
Grindflek &
Sehested
(1996)
Country
Norway
Holland
Holland
Scale
3 points
3 points
Breed
YY and LL
(Only Boars)
9 points
YY, LL, DL,
YL, LY and
commercial
Number of animals tested
Foreleg
11 500
6 333
Foreleg bone
0,469
0,06
Foreleg pasterns
0,474
0,31
Foreleg claws
0,042
0,09 - 0,15
Hind legs hock
Hind leg pasterns
0,011
0,23
Hind legs claws
0,067
0,30
foreleg wrist
0,133
0,09 - 0,15
Front view of forelegs
0,467
0,06
Rear view of forelegs
0,146
0,22
Locomotion
0,082
0,13
LL
YY
10 780
0,04 - 0,32
15 780
0,15 - 0,26
0,05 - 0,21
0,08 - 0,14
0,04 - 0,21
0,13 - 0,16
0,05 - 0,21
0,08 - 0,14
0,01 - 0,44
0,14 - 0,23
24