Litter Productivity in Large White Pigs: 2. Heritability and repeatability estimates

SUMMARY Estimates of the heritability, the repeatability and the genetic cor-relation coefficients of litter performance traits were calculated from data on 38000 Large White litters farrowed in 146 British herds. The repeatability estimates of number of live pigs per litter at birth, three weeks and eight weeks were 0·15, 0·14 and 0·14 respectively. The corresponding heritability estimates were 0·07±0·02, 0·07±0·02 and 0·09±0·03, respectively. The repeatability estimates of litter weight at three weeks and eight weeks were 0·15 and 0·04, while the corresponding heritabiUty estimates were 0·08±0·02 and 0·03±0·02. High positive genetic and phenotypic correlations were obtained between litter size and litter weight. A number of model culling schemes were considered and it was found that even at relatively high culling levels the improvement in overall herd mean performance was very small. Direct selection for litter size may yield a useful rate of improvement if selection is con-fined to one trait and large selection differentials are achieved, but could not be economically justified.