The nutrition of the early weaned lamb:I. The influence of protein concentration and feeding level on rate of gain in body weight

Abstract

SUMMARYThe live-weight gains of male and female lambs were measured during growth from 16 to 40 kg live weight when five cereal-based diets varying in dietary crude protein concentration (from 10 to 20%) were given at three levels in a 5×3×2 factorial design.Males grew faster than females by about 15% (P < 0·001); this difference increased with age and with the amount of feed given (P < 0·05). Growth rate responded linearly to increase in feeding level (P < 0·001) and curvilinearly to increase in dietary protein concentration (P < 0·01). A significant interaction (P < 0·01) occurred whereby growth increased with higher protein concentrations as feeding level increased.At the highest feeding level (near ad libitum) the results suggest that the optimum dietary crude protein concentration for growth was about 17·5, 15·0, 12·5 and 12·5% at body weights of 20, 25, 30 and 35 kg respectively. The overall optimum dietary crude protein concentration for growth between 16 and 40 kg body weight was about 17·0, 15·0 and 11·0% when the mean digestible energy intake was 3·0, 2·6 and 2·1 Mcal/day.The results agree reasonably well with estimates of protein requirements for lambs given by the Agricultural Research Council (1965).