Divergent selection on 63-day body weight in the rabbit: response on growth, carcass and muscle traits

The effects of selection for growth rate on weights and qualitative carcass and muscle traits were assessed by comparing two lines selected for live body weight at 63 days of age and a cryopreserved control population raised contemporaneously with generation 5 selected rabbits. The animals were divergently selected for five generations for either a high (H line) or a low (L line) body weight, based on their BLUP breeding value. Heritability ($h^2$) was 0.22 for 63-d body weight ($N = 4754$). Growth performance and quantitative carcass traits in the C group were intermediate between the H and L lines ($N = 390$). Perirenal fat proportion ($h^2 = 0.64$) and dressing out percentage ($h^2 = 0.55$) ranked in the order $\rm L < H = C$ (from high to low). The weight and cross-sectional area of the Semitendinosus muscle, and the mean diameter of the constitutive myofibres were reduced in the L line only ($N = 140$). In the Longissimus muscle ($N = 180$), the ultimate pH ($h^2=0.16$) and the maximum shear force reached in the Warner-Braztler test ($h^2=0.57$) were slightly modified by selection