GENETIC EVALUATION OF ON-FARM TESTED PIGS USING AN ANIMAL-MODEL .1. ESTIMATION OF VARIANCE-COMPONENTS WITH RESTRICTED MAXIMUM-LIKELIHOOD

Variance components of average daily gain (ADG) and premium cuts in proportion to carcass weight (PCP) estimated from ultrasonic measurements for on-farm tested Yorkshire and Landrace pigs in Switzerland were estimated by REML (restricted maximum likelihood) using an animal model. In order to keep computing costs reasonable, three subsets of data with at least 10 000 tested animals were sampled by herd from the complete data set for each breed. The single trait model contained fixed herd x year x season, sex, and unknown parent group effects and a linear regression on live weight, as well as random litter and animal effects. The estimated variance components from the data subsets were averaged within breed. Although the estimates from the different subsets varied considerably, the mean estimates were similar for both breeds and in agreement with values reported in the literature. For ADG the estimates of heritability (h2) were 0.16 and 0.20, and the estimates of the litter variance in proportion to the phenotypic variance (c2) were 0.42 and 0.49 for the Yorkshire and Landrace breed, respectively. For PCP h2 estimates for Yorkshire and Landrace pigs were 0.44 and 0.42, respectively, and c2 estimates were 0.16 for both breeds. The values found for phenotypic, genetic and litter correlations between ADG and PCP ranged from -0.12 to -0.24.