The effect on intake digestibility and microbial protein production of adding urea to rice straw for cattle and buffalo calves

摘要

Four cattle calves (Boss indicus) of average weight 120 kg and four swamp buffaloes calves of average weight 220 kg were fed four rice straw diets in a Latin square design. The rice straw were sprayed with 0%, 0.5%, 1% and 2% of urea and given ad libitum. Each period was 15 days during the last 5 days of which urine and faeces were collected. Urine samples were analysed for excretion of purine derivatives (PD) to measure microbial protein production. There was no significant effect on intake of rice straw which was 3.1, 3.4, 3.1 and 3.1 kg DM/day for cattle and 4.5, 4.5, 4.5 and 4.6 kg DM/day for buffalo. Rumen NH₃ concentrations were 39, 60, 70 and 96 mg/l for cattle and 51, 81, 102 and 132 mg/l for buffalo with significant difference. However the PD excretion in the urine was not significantly changed being 0.28, 0.19, 0.18 and 0.23 mmol/kg W0.75 for cattle and as expected lower for buffaloes being 0.13, 0.11, 0.12 and 0.11 mmol/kg W0.75. The dry matter digestibilities for cattle were 57.1, 60.3, 58.3 and 60.7 while for buffalo the digestibilities were 60.7, 57.4, 59.6 and 60.2. The results suggest that the rice straw containing 6% protein and digestibility between 57% and 60% provided sufficient crude protein for microbial needs.