Ruminal Characteristics, Blood pH, Blood Urea Nitrogen and Nitrogen Balance in Nili-ravi Buffalo (Bubalus bubalis) Bulls Fed Diets Containing Various Levels of Ruminally Degradable Protein

Four ruminally cannulated Nili-ravi buffalo bulls were used in a $4{\times}4$ Latin Square design to determine the influence of varying levels of ruminally degradable protein (RDP) on ruminal characteristics, digestibility, blood pH, blood urea nitrogen (BUN) and nitrogen (N) balance. Four isonitrogenous and isocaloric diets were formulated (NRC, 2001). The control diet contained 50% RDP. The medium (MRDP), high (HRDP) and very high (VHRDP) ruminally degradable protein diets had 66, 82 and 100% RDP, respectively. Increasing the level of dietary RDP resulted in a linear decrease in ruminal pH. A quadratic effect of RDP on ruminal pH was also observed with quadratic maxima at the 66% RDP diet. Dietary RDP had a quadratic effect on total bacterial and protozoal count with maximum microbial count at the 82% RDP diet. Increased microbial count was due to increasing level of ruminal ammonia nitrogen ($NH_3-N$). Increasing dietary RDP resulted in a linear increase in dry matter digestibility. Provision of an adequate amount of RDP caused optimum microbial activity, which resulted in improvement in DM digestibility. Increasing the level of dietary RDP resulted in a linear decrease in crude protein (CP) and neutral detergent fiber digestibility. Blood pH remained unaltered across all diets. A linear increase in ruminal $NH_3-N$ and BUN was noted with increasing level of dietary RDP. The increase in BUN was due to increased ruminal $NH_3-N$ concentrations. A positive N balance was noted across all diets. The results are interpreted to suggest that buffalo bulls can utilize up to 82% RDP of total CP (16%) with optimum results.