Methionine supplementation of milk proteins for preruminant lambs. I. Effect of protein concentration and source of carbohydrate on nitrogen balance

Abstract

Forty-seven crossbred lambs, aged 2–5 days at the start of the experiment, were used in three experiments. In experiment 1 a supplement of DL-methionine significantly increased the nitrogen balances of lambs given low or medium protein milk replacers based on cows' milk proteins. In experiment 2 the optimum level of supplementation of a low protein diet with DL-methionine was determined. Although the nitrogen balances were significantly increased by the supplement, the actual nitrogen balances at equivalent intakes of gross energy and nitrogen were less than those in experiment 1. The low protein diets in the two experiments differed only in the source of carbohydrate: lactose in cxpcrimcnt 1; lactose + glucose in experiment 2. In the final experiment 24 lambs in a 2 x 2 factorial design were fed on low protein diets containing casein as the source of protein, and lactose or glucose as the sole source of carbohydrate, with or without a supplement of DL-methionine. There was no significant effect of the source of carbohydrate on nitrogen balance.