Late gestational nutrient restriction: effects on ewes' metabolic and homeorhetic adaptation, consequences for lamb birth weight and lactation performance.

We investigated the effect of 50% nutrient restriction during the last 6 weeks of gestation on twin-pregnant ewes' plasma glucose, non-esterified fatty acid, beta-hydroxybutyrate, insulin, IGF-1 and leptin concentrations and the effects on lamb birth weight and ewes' lactation performance. Plasma metabolite and hormone concentrations in restricted ewes suggest that maternal tissues were being mobilised. Despite the ewes' adaptations their lambs weighed significantly less at birth. Furthermore, colostrum and milk yields were markedly reduced up until the latest measurement at 3 weeks post partum despite ad libitum access to feed. Reduced milk yields coincided with reduced plasma IGF-1 concentration pre partum in nutrient restricted ewes indicating, that mammary gland development may have been compromised. The present data suggest that leptin is not involved in the regulation of early lactation changes in feed intake and energy balance. It is concluded that severely reduced nutrient availability in late gestation affects fetal growth in utero and has a prolonged negative effect on lactation performance.