Offspring-sire regressions for production traits of pigs in a West Australian selection herd

Abstract

Results from farm performance tests of Landrace and Large White pigs were collected over 14 months in a nucleus herd in Western Australia. They were used to make offspring-sire estimates of heritability for average daily gain and two combined ultrasonic fat depths (CK fat). Pigs were tested at about 85 kg and average daily gain was estimated from birth. Only 60% of records from the offspring of homebred sires were analysed, together with the performance test records from all of these sires. Data were adjusted for breed, and then contemporary deviations were estimated as the deviation of a pig's performance from that of all his contemporaries. The offspring-sire heritability estimates accounted for the effects of breed and sex, with sums of squares then being pooled, giving values of 0.05 ¦ 0.1 6 and 0.57 ¦ 0.15 for average daily gain and CK fat, respectively. Adjustments for body weight increased the estimates to 0.27 and 0.68 but with larger standard errors. These latter heritability estimates were very similar to the paternal half sib estimates. The means of all offspring of homebred and purchased boars indicated no advantage of purchased boars over homebreds in the Landrace breed. However, for Large Whites, the purchased boars were genetically superior in average daily gain and inferior in CK fat (by 2.1 and 0.9 a, respectively, in the performance of progeny). The heritability estimates from this study, applied to group-fed farm-tested pigs, suggest similar results to those from central tests or farm tests in Queensland. However, some attention should be given in tested pigs to variation in final liveweights, and possibly to a start weight at weaning instead of at birth.