Variance components estimation for farrowing traits of three purebred pigs in Korea.
OBJECTIVE
This study was conducted to estimate breed-specific variance components for total number born (TNB), number born alive (NBA) and mortality rate from birth through weaning including stillbirths (MORT) of three main swine breeds in Korea. In addition, the importance of including maternal genetic and service sire effects in estimation models was evaluated.


METHODS
Records of farrowing traits from 6,412 Duroc, 18,020 Landrace, and 54,254 Yorkshire sows collected from January 2001 to September 2016 from different farms in Korea were used in the analysis. Animal models and the restricted maximum likelihood method were used to estimate variances in animal genetic, permanent environmental, maternal genetic, service sire and residuals.


RESULTS
The heritability estimates ranged from 0.072 to 0.102, 0.090 to 0.099, and 0.109 to 0.121 for TNB; 0.087 to 0.110, 0.088 to 0.100, and 0.099 to 0.107 for NBA; and 0.027 to 0.031, 0.050 to 0.053, and 0.073 to 0.081 for MORT in the Duroc, Landrace and Yorkshire breeds, respectively. The proportion of the total variation due to permanent environmental effects, maternal genetic effects, and service sire effects ranged from 0.042 to 0.088, 0.001 to 0.031, and 0.001 to 0.021, respectively. Spearman rank correlations among models ranged from 0.98 to 0.99, demonstrating that the maternal genetic and service sire effects have small effects on the precision of the breeding value.


CONCLUSIONS
Models that include additive genetic and permanent environmental effects are suitable for farrowing traits in Duroc, Landrace, and Yorkshire populations in Korea. This breed-specific variance components estimates for litter traits can be utilized for pig improvement programs in Korea.
Department of Animal Science and Technology, Sunchon National University, Suncheon 57922, Korea.
Bryan Irvine
BI
Lopez
Department of Animal Science and Technology, Sunchon National University, Suncheon 57922, Korea.
Tae Hun
TH
Kim
Department of Animal Science and Technology, Sunchon National University, Suncheon 57922, Korea.
Milton Tinashe
MT
Makumbe
Department of Animal Science and Technology, Sunchon National University, Suncheon 57922, Korea.
Chol Won
CW
Song
Department of Animal Science and Technology, Sunchon National University, Suncheon 57922, Korea.
Kang Seok
KS
Seo
Farrowing Traits; Purebred Pigs; Variance Components