Altering ewe nutrition in late gestation: II. The impact on fetal development and offspring performance

The present study was conducted to evaluate the effects of offering Belclare X ewes a single diet rationed to 80, 100, or 120% of recommended ME requirements from d 119 of gestation to parturition, with concurrent changes in other dietary nutrients. The effects on the development of the fetus and subsequent offspring performance to weaning were monitored. Sixty twin-bearing ewes were allocated to 1 of 3 dietary treatments based on Agricultural and Food Research Council recommendations (AFRC, 1993) as amended by Robinson et al. (2002a) as follows: 80% of predicted ME requirement, 100% of predicted ME requirement, and 120% of predicted ME requirement. Ewes were individually fed for the final 4 wk of gestation. Diets fed were grass silage based; however, when silage intake failed to meet ME requirements, ewes were offered varying quantities of concentrates, on an individual basis, to ensure they met their required daily ME allocation. Concentrates offered were composed of 40% barley, 22% beet pulp nuts, 20% distillers’ dried grains, and 14% soybean meal, on a DM basis. At birth, lambs were weighed, behavioral and skeletal measurements were recorded, and plasma blood samples were collected. At 1 h postpartum, a subset of lambs (n = 10) per treatment was euthanized to assess organ weight and intestinal morphology. At birth, there was no effect of treatment on lamb live weight at birth (P = 0.31), although lambs born to ewes offered 120% ME had a larger thoracic circumference (P = 0.05). Lambs born to ewes offered the excess energy treatment (120% ME) were quickest to stand and attempt to suckle after birth, in addition to having a greater live weight at weaning (P = 0.01) and ADG from birth to weaning (P = 0.05). Nutritional treatment had no effect on the organ weights (P ≥ 0.11) or the ileal morphology (P ≥ 0.62) of the lamb measured at 1 h postpartum. In summary, the impact of applying a dietary alteration to ewes in late gestation is not directly reflected in organ weight or total live weight at birth but is present at weaning, therefore outlining the poor reliability of using birth weight as an indicator of maternal nutrition during late gestation.