RELATIONSHIP OF DECREASED CECAL UREASE ACTIVITY BY DIETARY PENICILLINTO NITROGEN-UTILIZATION IN CHICKENS FED ON A LOW-PROTEIN DIET PLUS UREA

1. The relationship of the decreased caecal urease activity by dietary penicillin to nitrogen utilisation was assessed in chickens fed a low protein diet plus urea. 2. Dietary penicillin at 20 and 100 mg/kg dec reased anaerobic bacteria counts, urease activity and ammonia concentr ation in caecal contents (P < 0.05, except for ammonia in the case of the 100 mg/kg penicillin diet). 3. The 20 mg/kg penicillin diets signi ficantly increased the excretion of urea and total nitrogen (P < 0.05) and decreased ammonia excretion, and significantly reduced nitrogen r etention (P < 0.05). The 100 mg/kg penicillin diet also resulted in si milar but not significant changes, which tended to be less than those by the 20 mg/kg penicillin diet. 4. Ammonia, urea, glutamine and uric acid concentrations in blood, liver and kidney were unchanged by dieta ry penicillin. 5. It is concluded that caecal ammonia production from urea was closely correlated with nitrogen utilisation in chickens fed a low protein diet plus urea.