Partition of nitrogenous substances in the urine of sheep on different dietary protein intakes.

The distribution of nitrogenous substances in urine was studied in sheep fed high (28.71 g N daily) and low (9.32 g N daily) protein diets for 6-8 weeks. The concentrations of total nitrogen and urea, allantoin, free amino acids, uric acid, hippuric acid, creatinine, creatine and ammonia were measured in urine. The nitrogen content of these measured substances was calculated. The results showed that the concentrations of total urinary nitrogen and nitrogen of individual nitrogenous substances were lower in sheep on a low protein diet, except for uric acid nitrogen which was unchanged. Urea nitrogen was responsible for up to 74% of the total urinary nitrogen of both groups of animals without any significant difference. The individual nitrogen portions of nitrogenous substances other than urea in total urinary-N did not exceed 7% during the intake of both diets. The intake of a low protein diet resulted in a significant increase in the proportion of nitrogen from uric acid, hippuric acid, creatinine and free amino acids, while the fraction of ammonia nitrogen in the total urinary N was significantly reduced. It is concluded that different protein or nitrogen intake in the diet do not have any significant effect on the urea nitrogen fraction in the total urinary nitrogen of sheep.