Effects of early pregnancy to mid pregnancy nutrition of ewes on ewe and lamb liveweight and body composition, and on milk intake by lambs

SUMMARY Three groups of grazing ewes were managed so that over the period from 30 days before mating until day 100 after the start of mating, they would either gain (H), maintain (M) or lose (L) maternal weight. By day 100, the nutritional treatments had resulted in a range (H v. L) of 8-9 kg in ewe liveweights (including conceptus), but a much larger relative range in body energy reserves. The groups grazed together for the last 50 days of pregnancy, with ad libitum access to pasture. After lambing in early August, ewe and lamb liveweights and body compositions, and milk intakes by lambs were measured commencing on days 9, 23, 44, 69 and 86 of lactation. The H ewes produced more milk than L ewes during lactation, but mobilised more body fat and protein, so that ewe liveweights were similar by the end of the study. Lamb liveweight gains in the L treatment were significantly lower than in the H and M treatments (H 223, M 214, L 188 g/day). Changes in lamb body composition reflected their liveweight responses. The results are discussed in relation to the nutrition of the breeding ewe.