HETEROSIS, MATERNAL AND DIRECT EFFECTS FOR POSTWEANING GROWTH TRAITS AND CARCASS PERFORMANCE IN RABBIT CROSSES

A crossbreeding experiment was carried out in Egypt using a local bree d (Baladi Red, BR) and New Zealand White (NZ) to estimate direct heter osis, maternal additive effects and direct sire effects on some growth and carcass traits in rabbits. Data of body weight (at 5, 6, 8, 10, 1 2 weeks) and daily gains (at intervals of 5-6, 6-8, 8-10, and 10-12 we eks) on 2153 weaned rabbits were collected. Carcass performance at 12 weeks of age (weight and percentages of carcass, giblets, head, fur, b lood and viscera) on 213 male rabbits was evaluated. Estimates of coef ficients of variation (CV) for most growth and carcass traits were hig h and ranged from 10.0 to 40.2 %. Sire-breed was of considerable impor tance in the variation of growth traits and some carcass traits, while dam-breed contributed little. Sire-breed x dam-breed interaction affe cted (P<0.01 or P<0.001) most body weights and gains studied, while it contributed little to the variation of carcass traits. The purebred N Z resulted in rabbits with heavier weights and carcass and with lighte r non-edible carcass (blood and viscera) compared to the BR. Heterosis percentages for most growth traits were significant and ranged from 2 .5 % to 5.0 % for body weights and from 0.7 % to 9.5 % for daily gains . Insignificant positive direct heterosis was observed for most carcas s traits. Crossbred rabbits from NZ sires with BR dams were superior t o from the reciprocals. Maternal-breed effects on most weights and gai ns were insignificant, while sire-breed contrasts for some weights and gains proved significant. Postweaning growth and carcass performances of BR-mothered rabbits generally surpassed the NZ mothered, while NZ- sired rabbits were superior at later ages. High edible carcass was obs erved for BR-sired rabbits, while more non-edible carcass wastes (bloo d and viscera) for NZ-sired rabbits. Maternal-breed effects appeared t o be less important than paternal-breed effects in influencing most we ights, gains and carcass traits studied.