Body composition changes and energy retention in milk-fed lambs undergoing energy restriction

Eighteen milk-fed Churra lambs were used to study the effect of three levels of energy intake below maintenance requirements (293, 377 and 460 M GE/kg body weight (BW)(0.75)) at different BW (LW: 5 kg; HW: 8 kg) on energy retention (ER) and mobilisation of body components. Losses of fat and energy were related to energy intake (linear orthogonal contrast; p<0.05). Energy and fat mobilisation were greater for HW (linear contrast, p<0.05). There was also a significant effect of energy intake on protein retention, with increased protein deposition at higher energy intakes (linear contrast, p<0.05). Crude protein retention for the LW group ranged from negative (for the lowest level of energy intake) to positive mean values, while the mean values for the HW group were always greater and positive. No evidence of maintenance energy requirements changing quantitatively during the milk-fed phase was found in this study. Daily NE requirements for maintenance were not significantly different (p>0.05) for LW and HW groups either, the overall value being 494 kJ/kg BW0.75 (SE 74.4). (C) 1999 Elsevier Science B.V. All rights reserved.