Model Selection and Genetic Parameter Estimation for Performance Traits, Body Measurement Traits and Leg Score Traits in a Closed Population of Duroc Pigs

Abstract

During the course of developing a strain of Duroc pigs, 1, 381 pigs were used to determine the growth rate from birth to the day at 30kg, the growth rate during the period from 30 to 90kg of body weight, the back fat depth, the eye muscle area and leg scores when the body weight was approximately 90kg. Additionally, body size was measured at 90kg body weight. The pigs were allowed free access to the diet. The contemporary group and gender as the fixed effects, the sire and dam as the random effects and end test weight as a covariate were taken into the mathematical model for the analysis of the data. Genetic parameters were estimated by the animal model restricted maximum likelihood (REML) method. The effect of contemporary group categorized on the basis of the test date was significant for all of the traits measured on the test starting date and thereafter. The mathematical model which contains the contemporary group of one-week period tended to show a better Akaike's Information Criterion (AIC) than groups of two and four-week period. Significant differences between genders (boar, gilt, barrow) were observed in most of the traits. The effect of end test weight as a covariate was significant in all of the traits measured at approximately 90kg body weight. Estimates of the heritability of performance traits and body measurement traits generally varied from moderate to high. The heritability of leg score traits was low. Although an unfavorable genetic correlation between back fat depth and leg score traits was observed, the genetic correlation between leg score traits and daily gain during the period from 30 to 90kg of body weight was favorable. The results suggest that the simultaneous improvement of the growth rate and leg score traits is not difficult in Duroc pigs, but there might be difficulty in the improvement of obtaining less back fat depth and better leg soundness.