Consequences of maternal nutrition during pregnancy and of fetal growth for productivity in sheep

Severe, chronic growth retardation in utero resulting in very low birth weight may reduce mature size and increase fatness of sheep. However, effects of moderate maternal nutritional restriction or foetal growth retardation may not persist. Consequences of foetal growth retardation may be exacerbated or ameliorated by the early postnatal environment. Maternal nutrition during early- to mid-pregnancy has variable affects on postnatal growth and composition of lambs, and it remains unclear whether effects during this period are caused by direct effects on the foetus mediated by altered maternal nutrition or by indirect effects mediated via the dam during lactation. A limited number of studies with sheep have not shown long-term effects of nutrition during pregnancy or of foetal growth on postnatal efficiency of nutrient utilisation. Long-term effects of altered maternal nutrition or foetal growth on eating quality have not been demonstrated. However, nutrition during pregnancy, particularly during late-pregnancy, can alter wool production. Furthermore, nutrition during early life may influence subsequent reproductive performance of sheep. There is no evidence to suggest that lactational performance is affected by maternal nutrition during pregnancy or by foetal growth. Adequate feeding of ewes during late pregnancy and lactation to ensure that foetal and neonatal growth is not seriously compromised will help to optimise lamb performance. However, the potential of nutritional and other treatments during early pregnancy to enhance productivity has yet to be realised.