Effects of Dietary Protein on Nitrogen Metabolism and Protein Requirements for Maintenance of Growing Thai Swamp Buffalo (Bubalus bubalis) Calves

The experiment was conducted to investigate the effect of dietary crude protein on nitrogen utilization, nutrient digestibility and protein requirement for maintenance of swamp buffalo calves. Four growing swamp male buffaloes with 12-18 months old (average initial weight 209 +/- 17 kg) were used. The calves were assigned to use a 4x4 Latin square design to receive four diets. In terms of treatment, Crude Protein (CP) levels in the diets were 5, 7, 9 and 11% of Dry Matter (DM) and all diets were isocaloric (20% above maintenance of ME). CP intake and CP digestibility of calves clearly increased (p<0.05) with increasing CP content in diet. However, increasing the levels of dietary protein did not significantly alter (p>0.05) DM intake, digestibility of DM, organic matter, neutral detergent fiber and acid detergent fiber, body weight change and ruminal pH in calves. As the level of CP in diet increased, blood urea nitrogen, ruminal ammonia N, total volatile fatty acid, urinary N, N retention and N balance were observed to increase linearly (p<0.05). While N fecal was not significantly different (p>0.05), when dietary protein. levels increased. The relationship between N Balance (NB) and N intake (NI, g kg(-1) W-0.75) in swamp buffalo calves was NB = 0.883NI-0.653 (R-2 = 0.855). Present findings suggested that nitrogen requirements for maintenance of growing Thai swamp buffalo calves were 0.74 g N or 4.63 g CP kg(-1) BW0.75.