COMPARISON OF DUROC AND BRITISH LANDRACE PIGS AND THE ESTIMATION OF GENETIC AND PHENOTYPIC PARAMETERS FOR GROWTH AND CARCASS TRAITS

Duroc and halothane negative British Landrace boars and gilts were performance tested on ad libitum or restricted feeding regimes, with like-sexed non-littermate groups of one, two, three or four pigs per pen. There was a total of 320 pigs with 20 litter groups per breed with four boars and four gilts per litter group. Within each feeding regime, a boar and a gilt from each litter were tested on one of two diets in 1986, for each of the four combinations, and pigs were tested similarly for two other diets in 1987. Carcass composition was determined by half-carcass dissection of 160 pigs allocated between treatments. There was a breed × sex interaction for growth and performance traits for pigs fed ad libitum. Duroc boars were faster growing and more efficient than Landrace boars, but Duroc gilts grew more slowly and were less efficient than Landrace gilts. On restricted feeding, Duroc pigs were more efficient than Landrace pigs. At constant slaughter weight, Duroc pigs had less subcutaneous fat but more intermuscular fat. Although they had less separable fat in the carcass, Duroc pigs were not leaner as weights of bone, skin, head, feet and tail were heavier than for Landrace pigs. Group penning and group feeding of pigs may have enhanced competition effects resulting in positive genetic and phenotypic correlations between growth rate and backfat depths on both feeding regimes. The positive genetic correlation between growth rate and fat deposition resulted in a negative genetic correlation between growth rate and carcass lean content and a lower genetic correlation with lean tissue growth rate than in other studies. © 1990, British Society of Animal Science. All rights reserved.