A study of protein requirements of housed Scottish Blackface ewes during late pregnancy

SUMMARY In-lamb ewes were given 38, 58 and 82 g of digestible crude protein daily at a constant energy intake of 1600 kcal ME per head daily during the last 6 weeks of gestation. There were no significant differences between treatments in live-weight gain of the ewes, lamb birth weight or ewe net body-weight change (the difference between live-weight gain over the experimental period and live-weight loss at lambing). Digestibility coefficients for the diet components and nitrogen balances were determined on three ewes per treatment during weeks 15-16 and 19·20 of gestation. No differences in the apparent digestibility of the diet components were observed between the two periods. The apparent digestibility of crude protein increased significantly (P > 0·001) with increase in crude protein intake. A significant linear relationship (P<0·01) was found between digestible crude protein intake and nitrogen retention; daily N retention increased by 0·19 g per kg W0·73 for every 1 g per kg W0·73 of apparent digested nitrogen intake per day.