ADDITIVE GENETIC AND MATERNAL EFFECTS ON POSTWEANING GROWTH AND CARCASS TRAITS IN RABBITS

Additive genetic and maternal effects were estimated for postweaning g rowth traits and carcass traits using a derivate-free REML procedure u nder animal model. The traits studied were weight at 84 days of age, a ge at slaughter, postweaning ADG, dressing percentage, weight of kidne y and pelvic far, and muscle pH value and electrical conductivity in t he semimembranosus muscle. Heritability estimates from a total of 728 rabbits in a reciprocal crossbreeding experiment ranged from 0.15 to 0 .26 for postweaning growth traits, 0.21 for dressing percentage, 0.38 for weight of kidney and pelvic fat, 0.02 for pH value, and 0.51 for e lectrical conductivity. Considerable maternal effects were present in postweaning growth traits and in weight of kidney and pelvic fat. Gene tic correlation estimates indicated that genetic selection for postwea ning daily gain would lead to lower dressing percentages (-0.51) and l eaner carcasses (-0.34). The genetic relationships between ADG after w eaning and pH value (-0.90), and between ADG and electrical conductivi ty (0.58) illustrated a shifting towards a glycolytic energy metabolis m of the muscle due to increased growth. Litter size at birth was foun d to be a significant source of variation for all postweaning growth t raits (p < 0.001) and for electrical conductivity (p < 0.05). Genetic selection for litter size at birth would result in decreased growth ra tes, lower dressing percentage and enhanced adiposis.