GROWTH PERFORMANCE FOR FOUR BREEDS OF SWINE: CROSSBRED FEMALES AND PUREBRED AND CROSSBRED BOARS

Purebred and two-breed cross (F1) boars were mated to F1 females to produce all possible three- and four-breed cross pigs involving the Duroc, Yorkshire, Landrace and Spotted breeds. Individual post-weaning average daily gain (ADG), age at 100 kg (AGE) and probed backfat thickness at 100 kg (BE) data were collected on 3,456 pigs. A total of 213 pens with an average of 15.58 pigs per pen was evaluated for post-weaning feed-to-gain ratio (F/G) and average daily feed consumption (ADF). Genotype x environment interactions, specifically breed x year-season farrowed and breed X parity (for ADG), were found to be highly significant. Certain results, however, were reasonably consistent across environments. Duroc-sired pigs grew more efficiently than other sire breed groups (3.11 vs 3.21 F/G), although there were no significant differences in ADF between sire groups. Duroc-sired pigs had less BF than other three-breed cross pigs, based upon within breed of dam comparisons, suggesting differences in composition between the more efficient Duroc-sired pigs and other breed groups. Landrace-sired pigs were fatter than other sire groups. No real differences between crossbred-sired pigs and the average of contemporary purebred- sired pigs were apparent for F/G, ADF, ADG, AGE or BF. Assuming paternal heterosis to be zero, these results suggested recombination effects to be negligible for postweaning performance traits. Apart from via direct genetic effects, mating crossbred rather than purebred boars to females of different breeding should have little or no impact on feedlot performance of offspring produced