PROTEIN EVALUATION IN RUMINANTS .2. EVALUATION OF AGROINDUSTRIAL BY-PRODUCT-BASED RATIONS IN METABOLIC AND RUMEN STUDIES OF BUFFALO CALVES

Six growing male buffalo calves fitted with a rumen fistula were fed a 40% wheat straw and 60% concentrate mixture containing urea (basal di et), groundnut cake (GNC), mustard cake (MC), cottonseed cake (CSC), g uar meal (GM) or sun-dried poultry excreta (PE) as a supplementary pro tein source in a 6X6 Latin square design. The dry matter intake was ke pt constant for all the diets. Six metabolic trials were conducted whi le allowing the switch over every 32nd day. After every trial, rumen l iquor samples were collected for 3 consecutive days at 0, 1, 2, 4 and 6 h after feeding. There was no difference (P<0.05) in the crude prote in digestibility of isonitrogenous diets based on different natural pr otein sources, i.e. GNC, MC, CSC and GM. The crude fibre digestibility was not affected by the different protein supplements (P<0.05) althou gh it appeared to be less with the supplementation of CSC. The crude f at digestibility was found to be more (P<0.05) on oilseed cake diet co mpared with the GM, PE and basal diets. Urinary-N excretion was signif icantly higher with the GNC diet and less with the GM and PE diets com pared with the MC and CSC diets. The mean pH of the strained rumen liq uor (SRL) was almost the same on the test diets (7.28-7.33), but was s ignificantly less (P<0.05) for the basal diet (7.20). An increase in t he total-N (mg per 100 ml SRL) concentration observed at 1 h postfeedi ng was least for the GM diet and maximum for the CNC and CSC diets, wh ereas the mean level of total-N from GNC, MC and GM did not differ sig nificantly (P<0.05) from one diet to another (110.2, 105.2 and 109.2 m g per 100 ml SRL). Also, in the case of GM, there was a slow decline i n N concentration at 2 and 4 h postfeeding compared with GNC and MC. T he protein-N concentration (measured as TCA-N) (trichloroacetic acid p recipitate-N) ranged from 53.7 to 66.0 mg per 100 ml SRL and the diffe rences between various protein sources were significant (P<0.05). The higher level of the non-protein-N fraction in the SRL for the GM and P E diets observed at 4 h postfeeding was attributed to the higher level of amino-N. The mean NH3-N concentration ranged from 22.4 to 35.6 mg per 100 ml SRL and was significantly higher for the diet at all times. It appeared that the rate of release of NH3 for GNC was more than its incorporation into microbial protein, thereby resulting into its net loss via the urine. The results also indicated that GM protein degrada tion was of a continuous nature which encouraged greater utilization o f NH3-N for the synthesis of microbial-N.