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Concentrate protein source impacts on animal performance

Dr Tim Keady

A recent study was undertaken at Athenry to evaluate the effect of source of concentrate protein, and concentrate feed level on the performance of ewes in late pregnancy and the performance of their progeny. In late pregnancy ewes were offered either low (16 and 21 kg for twins and triplet bearing ewes) or high (28 and 32 kg for twin and triplet bearing ewes) concentrate feed levels. Two concentrates were formulated using two different sources of protein namely soyabean meal and by-products. The main protein sources in the by product based concentrate were rapeseed meal, distillers grains and maize gluten feed. The concentrates were formulated to have the similar protein (18%) and metabolisable energy (12.4 mj/kg DM) concentrations. The ewes had been housed in early December, shorn and offered grass silage (DMD 74%) ad-lib until lambing.

The soyabean based concentrate increased lamb birth weight by 0.36 kg and lamb live weight gain from birth to 5 weeks by 22 g/day. Subsequently, lambs from ewes offered the soyabean based concentrate were 0.8 kg heavier at weaning. Increasing concentrate feed level in late pregnancy had no effect on lamb birth weight or subsequent lamb performance. It is concluded that altering the protein source in the concentrate offered to ewes in late pregnancy, even when formulated to concentrate similar crude protein and metabolisable energy concentrations, had a greater effect on lamb performance than increasing concentrate feed level by 75% for twin bearing ewes. Therefore concentrate ingredient composition is more important than feed level.