Prenatal undernutrition can have a permanent ‘programming’ effect on offspring growth, health, behaviour and reproductive ability that persists into adulthood (Meaney et al., 2007; Bell, 2006). However, whether different genotypes are equally affected is unknown. Relatively slower growing breeds of sheep, that are adapted to poorer food availability in pregnancy (such as the Scottish Blackface) may be better able to buffer their developing foetuses from the effects of undernutrition in utero than faster growing breeds, such as the Suffolk. In this experiment we investigated whether a 25% reduction in food intake for the first 90 days of gestation would result in differential responses in these two breeds of sheep.