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Estimates of variance components for swine litter quality traits
The objective of the study was to estimate variance components for swine litter quality traits, including three new litter traits; number of piglets weaned weighing ≥ 3.2 kg (QWP), CV for piglet birth weight (CV_BWT) and CV for piglet weaning weight (CV_WWT).Reproductive data and pedigree information were obtained for Landrace (n=5407) and Large White (n=5825) litters from Smithfield Premium Genetics. Litter traits included total number born (TNB), number born alive (NBA), litter birth weight (BWT), CV_BWT, number weaned (NW), QWP, litter weaning weight (WWT) and CV_WWT. Variance components and genetic correlations were estimated with ASReml using two trait models. All models included fixed effects of contemporary group (herd × year × month), parity, a covariate of age at first farrowing and a random effect of sow. Models for BWT and WWT also included NBA and NW, respectively, as a covariate. Heritability estimates for TNB, NBA, BWT, CV_BWT, NW, QWP, WWT and CV_WWT for Landrace were 0.11, 0.11, 0.17, 0.05, 0.09, 0.11, 0.26 and 0.08, respectively and for Large White were 0.14, 0.09, 0.11, 0.01, 0.08, 0.11, 0.12 and 0.03, respectively. Phenotypic variance estimates for TNB, NBA, BWT, CV_BWT, NW, QWP, WWT and CV_WWT for Landrace were 9.56, 8.77, 47.2, 34.2, 15.51, 5.95, 757.0 and 42.6, respectively and for Large White were11.55, 11.87, 49.7,35.92, 10.26, 7.99, 967.8 and 45.0, respectively. Genetic correlations between litter quality traits for both Landrace and Large White are shown in Table 1. Results suggest that selection for TNB may increase litter variation in birth and weaning weight. However, selection for QWP may decrease litter variation in birth weight for Landrace and reduce litter variation in weaning weight for both Landrace and Large White.
Table 1. Genetic correlations between litter quality traits for Landrace (above diagonal) and Large White (below diagonal). |
||||||||
|
TNB |
NBA |
BWT |
CV_BWT |
NW |
QWP |
WWT |
CV_WWT |
TNB |
|
0.87 |
-0.22 |
0.29 |
0.27 |
0.47 |
0.10 |
0.12 |
NBA |
0.95 |
|
0.52 |
0.20 |
0.45 |
0.67 |
-0.03 |
0.09 |
BWT |
-0.67 |
0.64 |
|
-0.24 |
-0.04 |
0.16 |
0.50 |
-0.23 |
CV_BWT |
0.29 |
0.01 |
-0.39 |
|
0.14 |
-0.07 |
0.14 |
0.31 |
NW |
0.51 |
0.96 |
-0.04 |
0.39 |
|
0.99 |
0.61 |
-0.46 |
QWP |
0.54 |
0.99 |
0.02 |
0.23 |
0.98 |
|
0.68 |
-0.29 |
WWT |
-0.25 |
0.05 |
0.68 |
-0.37 |
0.98 |
0.95 |
|
-0.44 |
CV_WWT |
0.04 |
-0.15 |
-0.10 |
-0.28 |
-0.53 |
-0.66 |
-0.89 |
|
Keywords: genetic, reproduction, sow