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Animal Science Departmental Report 2004-2005 Return to Swine articles
Estimation of Genetic Parameters for Reproductive Traits between First and Later Parities S.
H. Oh, D. H. Lee1 and M. T. See 1Hakyong
National University, Ansung, Korea Introduction Separation of gilt and sow records as different reproductive traits should be considered because females differ in physiological development of reproductive organs at differing parity. If repeatability is high, that is, the correlations between parities are highly related, it would be desirable that all parities be considered as one trait. However, if repeatability is low it is appropriate that measures from differing parities be analyzed as independent traits including. A second reason would be because the analyses are more accurate and computationally faster. The objective of this study was to estimate genetic parameters between the first and later parities as different traits for reproductive traits of pigs using multiple traits animal model. Materials and MethodsData
consisted of reproductive traits from Gaya farm in South Korea, and there are
total 2371 individuals in the pedigree file. Sire and dam consisted of three
breeds, respectively. The first and later records were considered as two
different traits when analyzing data. The traits include in the analyses were
total pigs born (TB1), number of pigs born alive (NBA1), number of pigs weaned (NW1),
and litter weaning weight (LWT1) in the first parity, and total pigs born (TB2),
number of pigs born alive (NBA2), number of pigs weaned (NW2), litter weaning
weight (LWT2) and interval between farrowing events (FTF) in later parities. Age at farrowing in months was calculated as a division of
days from birth to farrowing date by 30.45, and days to return to estrus was
calculated as days from farrowing to the last breeding date. Days to weaning
was defined as days from farrowing to weaning date, and FTF was defined as days
from previous farrowing to present farrowing date. If the number of fostered
individuals was greater than total number of born alive, the data were deleted,
and if the number of weaned individuals was greater than the number of fostered
individuals, the data also were deleted. Records with total number born alive
less then two, or days to weaning less than five were removed. The model for first parity records included year-season, dam
breed, sire breed, farrowing month and days to weaning as fixed effects, and the
random genetic effect of animal. The model for later parity records included
fixed effects of year-season, parity, dam breed, sire breed, days from weaning
to estrus and days to weaning, and random genetic effect ofanimal and a random permanent
environmental effect. Variance components were estimated by the software that
used an EM-REML algorithm (REMLF90; Misztal, 2001). Results and DiscussionHeritablity estimates for each trait are
shown in Table 1. Heritability estimates of TB1, NBA1, NW1 and LWT1 in the
first parity were 0.27, 0.25, 0.16 and 0.20, respectively. For TB2, NBA2, NW2,
LWT2 and FTF in later parities, heritabilities were estimated as 0.15, 0.15,
0.08, 0.11 and 0.07, respectively. These results indicate that heritability
estimates for first parity traits were higher than for later parity traits. This
may be due in part to the inclusion of the permanent environmental effect in
the model fitted for later parities Genotypic and phenotypic correlations
are summarized in Table 1. Genetic correlations between sow reproductive traits
in the first parity and in the second and later parity were estimated as 0.89, 0.77, 0.58
and 0.66 between TB1 and TB2, NBA1 and NBA2,
NW1 and NW2, and LWT1 and LWT2, respectively. Phenotypic correlations between TB1 and TB2, NBA1 and NBA2, NW1 and NW2,
and LWT1 and LWT2 were estimated as 0.18, 0.15, 0.06 and 0.10, respectively.
Rydhmer et al. (1995) reported a
similar genetic correlation (0.77) between NBA in first and later parities. Genetic correlations between reproductive
traits within the first parity were estimated as 0.95, 0.78 and 0.62 between
TB1 and NBA1, TB1 and NW1, and TB1 and LWT1, respectively. Estimates of genetic
correlations between NBA1 and NW1, and NBA1 and LWT1 were 0.86 and 0.74,
respectively. Estimates of genetic correlations between reproductive traits for
later parities were 0.96, 0.36 and 0.06 between TB2 and NBA2, TB2 and NW2, and
TB2 and LWT2, respectively. Estimates of genetic correlations between NBA2 and
NW2, NBA2 and LWT2, and NW2 and LWT2
were 0.26, 0.02, and 0.87, respectively. These results indicate that genetic correlations between traits in later
parities tended to be lower than those
observed among traits in the first parity. Genetic correlations between FTF and
other reproductive traits were found to be higher in later parities than in the
first parity. Estimates of genetic correlations between FTF and the first
parity traits TB1, NBA1, NW1 and LWT1 were 0.04, 0.02, 0.23 and 0.04,
respectively. Estimates of genetic correlations between FTF and later parity traits
TB2, NBA2, NW2 and LWT2 were 0.21, 0.12, 0.20, and 0.28, respectively. Conceptually, it is easy to think that
genetic correlations between traits of the first and later parities in sows
would be one, however, the results of this study indicate that these genetic
correlations are not high enough to consider first and later parity records as
one trait. Generally the first three parities have high genetic correlations
(Haley et al., 1988), but the genetic correlation between the first and the
fourth and greater parities could be lower due to the effects of selection or
environment (Roehe and Kennedy, 1995).
In other words, it is suitable that traits in the first parity and in later
parities should be considered as different traits due to the effect of
selection, permanent environment, previous parities affecting the subsequent parities
of sows. Statistics
of breeding values for each reproductive trait from the nine-multiple traits
analyses are presented in Table 2. Means of estimated breeding values of
reproductive traits in the first parity were, respectively, -0.062, -0.060, -0.045
and -0.383 for TB1, NBA1, NW1 and LWT1. In later parities, means of estimated
breeding values were, respectively, -0.045, -0.039, -0.009 and -0.064 for TB2,
NBA2, NW2 and LWT2. In the mean time, the standard deviations of breeding
values had a trend to decrease in the second and later parity rather than in
the first parity. For breeding values, estimates of
later parities were higher than for first parity in all traits. Also, standard
deviations of breeding values in later parities were less than in the first
parity. This is in agreement with the heritability estimates of later parities being
less than those for the first parity. ConclusionGenetic correlations between reproductive traits of the first
and later parities were not as high as expected. This indicates that
reproductive traits of the sow should be analyzed considering first and later
parities as different traits. The genetic correlations between productive and
reproductive traits in the first and later parities should also be be analyzed to
compare the impact of correlated response and selection programs. ReferencesHaley, C. S., E. Avalos, and C. Smith.
1988. Selection for litter size in the pig. Anim. Breed. Abstr. 56:317. Misztal, I. 2001. BLUPF90 family of
programs. http://nce.ads.uga.edu/~ignacy/newprograms.html Roehe, R., and B. W. Kennedy. 1995.
Estimation of genetic parameters for litter size in Canadian Yorkshire and
Landrace swine with each parity of farrowing treated as a different trait. J.
Anim. Sci. 73:2959-2970. Rydhmer, L., N. Lundeheim, and K.
Johansson. 1995. Genetic parameters for reproduction traits in sows and
relations to performance-test measurements. J. Anim. Breed. Genet. 112:33-42.
*ns
= not significant TB1
= Total born parity 1, NBA1 = Number born alive parity 1, NW1 = Number pigs
weaned parity 1, LWT1 = Litter weaning weight parity 1, TB2 = Total born in
later parities, NBA2 = Number born alive in later parities, NW2 = Number pigs
weaned in later parities, and FTF = Farrowing to farrowing interval
TB1
= Total born parity 1, NBA1 = Number born alive parity 1, NW1 = Number pigs weaned
parity 1, LWT1 = Litter weaning weight parity 1, TB2 = Total born in later
parities, NBA2 = Number born alive in later parities, NW2 = Number pigs weaned
in later parities, and FTF = Farrowing to farrowing interval |