This work was conducted with the objective to determine the body composition for fat, protein and ash, the net requirements of energy and protein for weight gain, and the requirements of metabolizable protein of growing lambs. Twenty-two male lambs, sired by Texel males, from crossbreed Texel x Ideal dams were used. Four lambs were slaughtered at the beginning of the experiment (24 hours after birth) and groups of six lambs were slaughtered at weaning, at 28 and 33 kg of live weight. The prediction equations of the corporal composition of protein, fat, ash and energy were fitted, according to the ARC (1980), by the regression of log of fat, protein, ash and energy, content in the empty body, in relation to the log of empty body weight (EBW). The net requirements of protein and energy for weight gain were obtained based on the prediction equations of body composition, while of metabolizable protein requirements were estimated in agreement with the AFRC (1993). The body contents of protein, fat, energy and ash for lambs from 5 to 30 kg EBW. ranged from 141.69 to 186.24 g/kg EBW; 24.49 to 158.11 g/kg EBW; 1088.75 to 2451.55 Kcal/kg EBW, and 27.55 to 33.70 g/kg EBW, respectively. The estimated net requirements for weight gain were: energy, from 399.93 to 892.21 kcal/250g of gain, and protein from 40.98 to 53.70 g/250g of gain, for lambs from 5 to 30 kg of EBW, respectively. The requirements of metabolizable protein for animals from 5 to 30 kg live weight ranged from 79.09 to 121.13 g/250g of gain.
corporal composition; net requirement; sheep; weight gain
