Orotic acid and non-protein nitrogen overload in sheep

Experiments were conducted in sheep to investigate the protective effect of orotic acid versus acetic acid (0.2 g/kg body weight) against the effects of the administration of urea (0.5 g/kg) into the rumen. Blood ammonia levels, motility of the reticulo rumen and food intake were measured. The quantity of ammonia nitrogen produced in the rumen was only 162 +/- 21 mg NH3-N/100 ml 2 hours after the urea and orotic acid addition instead of 229 +/- 31 mg NH3-N for urea and acetic acid. The blood ammonia level was reduced by 47% when orotic acid was used instead of acetic acid. The long-lasting inhibition of the contractions of the reticulo-rumen by urea was restricted to 120 and 80 min by acetic and orotic acid respectively. The amount of food intake which was halved by urea was only reduced by 40.7% when both acetic acid and urea were administered. Reduction in the amount of food intake due to urea was suppressed by the administration of orotic acid.