Indian Journal of Animal Nutrition

The studies were conducted on two non-lactating Danish Friesian cows (775 kg) fitted with a permanent rumen fistula and a re-enterant cannula in the duodenum about 50 cm behind the pylorus. The animals were fed on five isocaloric rations containing 1 per cent urea (R₁), 23 per cent urea (R₂), 45 per cent urea (R₃), 15 per cent soybean meal (SBM) (R₄) and 25 per cent SBM (R₅), one after the other In a switch over manner, alongwith molasses (5 per cent) and NaOH (4 per cent) treated barley straw which were common to all rations. The CP per cent In the rations R₁ to K₅ were 83,13.0, 19.9, 12.6 and 19.4 respectively, thereby making ration R₂ isonitrogenous with rations R₄ and ration R₃ with ration R₅. DM intake and DM digested in the rumen were similar for all rations. On urea based ration (R₁ to R₃), the essential amino acids supply to duodenum was 2.64 to 8.57 times higher than present in feed. This was 1.04 to 1.48 times more on R₄ and 0.75 to 1.10 time higher on R₅ than feed amino acids. There was a net increase of all essential amino acids (g/kg) OM digested in the rumen, g/kg DM intake), the increase being higher for R₄ than R₅. The differences of net amino acid synthesis between R₂ and R₄ varied from 2.4 to 14.0 g/kg OM digested in the rumen. The greatest difference being for leucine, which was followed by lysine, valine, iso-leucine, phenylalanine, threonine, histidine and methoinine.