The effect of level of nutrition during pregnancy and during lactation on lamb and wool production of grazing sheep

Seven different experiments over 3 years and involving a total of 1750 ewes have been designed to study the effects of high and low levels of nutrition during pregnancy and during lactation on grazing sheep. The trials were run as nearly as possible under typical fat-lamb producing conditions. Commencing with breeding ewes in average store condition before tupping, a live-weight gain of 25–40 lb. from tupping to lambing was adopted as a standard of a high level of feeding and a gain of ± 5 lb. was considered to be a low level of feeding. Differential feeding was obtained by keeping the ewes on high-quality pasture as a high level of nutrition, and by stocking heavily on poor pasture as a low level. Under these conditions the following results were obtained: (1) Level of nutrition during pregnancy. The high level of nutrition during pregnancy increased birth weight by about 0.5 lb., but had little if any influence on the rate of growth and the weaning weight of the lambs, irrespective of the subsequent level of nutrition. The high level did not reduce ewe and lamb mortality and there was some evidence to the contrary when the high plane was applied early, leading to large live-weight gain.