Comparison of corn gluten products and a soybean-bran mixture as sources of protein for lactating Chios ewes

This study was conducted in order to evaluate the effects of substitution of a high degradable protein source, soybean meal (SBM), with low degradable, corn gluten meal (CGM), and to determine the effects of ruminally protected lysine (lys) on the performance of lactating ewes fed a ration calculated to be first-limiting in lys. Forty-two multiparous Chios ewes were examined in a 8-week study that started at parturition. Animals were fed in groups (14 ewes), with three isocaloric-isonitrogenous-isofibrous rations. Treatments were (A) SBM and wheat bran (SW), (B) CGM and corn gluten feed (GF), and (C) CGM and CGF plus 10 g/d lys (GFL). GF and GFL groups resulted in higher fat, protein and solids non-fat (SNF) content in milk, but SW group was associated with a tendency for higher milk yield compared to GF, somewhat mitigated by lys supplementation in group GFL. The daily production of protein was higher in SW than in GF, but this difference was eliminated by lys supplementation, suggesting that lys was limiting in GF ration. Treatments did not differ in exportation of energy in milk, assessed by fat corrected milk (FCM), which is consistent with similar growth rate of the lambs. The reduced blood glucose level in ewes consuming rations containing CGM may be due to high proportion in UP of those diets.