Derivation of Metabolic Faecal Nitrogen Excretion in Murrah Buffalo Calves Fed Graded Levels of Protein in the Diet

The objective of this study was to determine metabolic faecal nitrogen (MFN) content in Murrah buffalo calves using recoveries of faecal nitrogen from appropriate linear regression models involving total nitrogen intake, nitrogen balance and DM intake. Fifteen Murrah buffalo male calves were divided into 5 groups (BW=171 kg) and fed total mixed rations containing wheat straw, berseem and concentrate mixture in different proportions so that the dietary CP level was 5, 7.5, 10, 12.5 and 15% in groups T1,T2,T3, T4 and T5, respectively. The trial lasted for 75 days. Mean DMI was found to be 63.66±5.16, 93.32±2.30, 95.20±1.88, 105.45±0.90, 111.80±4.04 g/kg W0.75 in groups T1, T2,T3,T4 and T5 groups, respectively. ADG (g/kg W0.75) was (P<0.05) -2.21, 2.79, 6.82, 7.66, 7.95 in T1, T2, T3, T4 and T5 groups, respectively. DM digestibility increased (P<0.05) from 49.98 to 64.63 with increase in protein level. Nitrogen balance (g/day) was -3.84±0.49, 29.31±2.43, 68.49±9.06, 45.96±10.76 and 82.05±11.07 in T1, T2, T3, T4 and T5 groups, respectively. There was increase (P<0.05) in nitrogen balance from T1 to T5 (−0.13 to 0.92 g/100g DMI). MFN excretion from growing buffalo calves determined using regression of total nitrogen intake and N balance on faecal nitrogen outgo separately accounted for 0.33–0.35 g/100g DM intake.