Ewe nutrition and lamb growth
Clark, C. Fiona S.
1. The literature review initially describes foetal and placental growth and development. The following two sections present the effects of nutrition before mating and in early pregnancy, concentrating mainly on the effect on ovulation and lambing rate, and identify the lack of information on the effect on foetal lamb growth and birth weight.2. Aspects of nutrition, particularly during mid and late pregnancy are reviewed. The close relationship between energy and protein nutrition is recognised in relation to foetal growth.3. Finally, an account of nutritional effects on lactation is given and again emphasising the role protein and energy have to play. Methods of assessing milk yield are also described.4. The first experiment provided information on differences in maternal body composition, early foetal and placental growth and development brought about by high and low planes of feeding for ten weeks before mating and up till 90 days of gestation. The foetus weights were not different, but placenta and cotyledon weights were heavier ( p <0.05) for better nourished ewes. Liveweights of ewes differed by 27 kg, but energy contents differed by 479 MJ, or poorly fed ewes had half the reserves of well fed ewes.5. The second experiment provided information on changes in body composition as a result of high and low levels of nutrition before mating. Ewes received different amounts of protein and energy in late pregnancy. fiaternal body changes as well as thegrowth of foetuses and placentae were followed throughout this period. As in the first experiment the changes in energy were greater than would have been predicted from liveweight changes. Maternal composition was largely affected by treatment before mating. Lambs from ewes on high protein levels were approximately 1 kg heavier than lambs from ewes on low protein irrespective of energy level. Little effect was observed on the placenta as a result of treatment, but it increased in weight between 90 and 14-2 days of gestation.6. The third experiment provided information on the effect of increasing increments of fishmeal inclusion in the concentrate ration on ewe weight, milk yield and lamb birth weight and growth rate. The milk yield and growth rate recording ceased after four weeks of lactation. There was a significant difference of about 2 kg in the weight of twin lambs from ewes receiving concentrates with 0.15 and 0.2 fishmeal compared with those receiving barley alone. By weaning, after grazing on pasture, no differences in lamb weight were evident.7. The results are discussed, in the light of current research information and in relation to commercial practice.