Studies of weaned lambs before, during and after a period of weight loss. II Body composition

Lambs at pasture were weaned when nearly 15 kg, brought indoors and given a balanced diet. They were studied during growth from 15 to 25 kg, then underfed for 21 weeks, which caused their weight to return to 17 kg, and finally allowed to regain weight on ad libitum feeding. The recovery phase was not commenced until some sheep were no longer able to stand and feed. At about 15, 20 and 25 kg in each phase of the experiment, tritiated water (TOH) space was measured on all sheep, and some were slaughtered and the chemical composition of the body determined. Body composition estimated from TOH space agreed closely with that measured post mortem. Allowing for variation with weight, the composition of the empty body was affected slightly by under-nutrition and by compensatory growth, but there was no net effect of the whole cycle of events. The only clear effect of weight change on body composition was a reduction in the protein content (with corresponding increase in fat) during the later stage of weight loss.