Relative growth in rabbits: the effects of genetic line, diet and gender

The relative growth of different parts of the body and tissues was analysed using an allometric model. Animals were crossbred rabbits (males and females) from the mating of commercial lines HYLA-grand parental doe (HY-GPD) female with HYLA Coloured (HY-CO) or Grimaud (GR) males, both selected for the growth rate, or HY-GPD males, selected for weaning weight. They were fed on two different diet, mainly differing in their energy content, and the relative growth of the different parts of their body was assessed. The components with a nearly isometric growth pattern, which grew at the same mean rate as the rest of the body, were skin, chilled carcass and reference carcass; hind legs for retail cuts; and dorsal and carcass length for linear measurements. All allometric coefficients were calculated with respect to the slaughter weight, except percentage of hind leg inter-intramuscular fat (IIMF), which was calculated with respect to the weight of the hind leg. The components that showed early maturing were liver, kidneys, breast and rib viscera for offal and organs; head and breast and ribs for retail cuts; and bone and IIMF percentage of the hind leg. The components with late maturing were forelegs and loin for retail cuts, inguinal, scapular and perirenal fat, meat of the hind leg, and thigh and lumbar circumference length for carcass linear measurements. The GR line showed earlier growth for loin than the maternal HY-GPD line. In addition, the GR and HY-CO lines developed scapular and inguinal fat later than the HY-GPD line. For IIMF percentage, GR presented later growth than HY-CO and HY-GPD. The main effect of the diet was on liver development and on scapular fat: rabbits fed on the high-energy diet showed later liver and scapular fat growth