Effect of genetic origin, diet and weaning weight on carcass composition, muscle physicochemical and histochemical traits in the rabbit

Fifty rabbits originating from the crossing of one dam strain with three si re strains, Hy+, INRA 9077 and INRA 3889, were studied. The adult body weig hts of the sire strains were 5.1, 4.1 and 3.1 kg, respectively. After weani ng, the Hy+ and the INRA 9077 rabbits were fed either an H (11.99 MJ DEkg D M-1) or L diet (9.67 MJ DEkg DM-1). The INRA 3889 rabbits were fed only the H diet. In each of these five blocks, two weaning weights were studied and the rabbits were slaughtered when the average body weight of each block re ached 2.5 kg. Slaughter yield, carcass fatness and hindleg meat to bone rat io were determined. Muscular tissue was described using (I) physicochemical criteria (ultimate pH, L*a*b* colour) of the biceps femoris (BFE), tensor fasciae latae (TFL) and semimembranosus accessorius (SMA) muscles and (2) h istochemical characteristics of the longissimus lumborum muscle (LL) throug h computerised image analysis (fibre type composition, cross-sectional area ). At slaughter, the rabbits of INRA 3889 sire origin, which had the highes t degree of maturity (72%), gave the best slaughter yield (p < 0.01), the h eaviest reference carcass weight (p < 0.01), and highest LL proportion (p < 0.01), hindleg meat to bone ratio (p < 0.05) and fatness (p < 0.01); their LL muscle showed the lowest percentage of beta R fibres, while the cross-s ectional area of their muscular fibres was the highest (p < 0.05). When all sire x diet combinations were put together, the heavier the weaning weight , the lower the daily gain (p < 0.01) and the lightness (L*) of thigh muscl es (p < 0.05). The lower the DE content of the diet, the lower the growth r ate, the slaughter yield, the reference carcass weight (p < 0.01) and the c ross-sectional area of all types of muscle fibres of the rabbits of both Hy + and INRA 9077 sire origin. (C) 1998 Elsevier Science Ltd. All rights rese rved.