Urinary excretion of endogenous nitrogen metabolites in adult domestic cats using a protein-free diet and the regression technique.

The study was designed to determine urinary excretions of endogenous total, urea, ammonia and creatinine nitrogen in adult domestic cats. Endogenous urinary nitrogen metabolite excretions were determined by feeding adult cats a protein-free diet for 10 d or by regression to zero protein intake of the urinary nitrogen metabolite excretions of adult cats fed four levels of dietary protein. The mean (+/- SEM) endogenous total, urea and ammonia nitrogen excretions for the cats fed the protein-free diet were 360 (+/- 11.3), 243 (+/- 8.8) and 27.6 (+/- 1.06) mg x kg body weight(-0.75) x d(-1), respectively. Estimates of 316 (+/- 53.9), 232 (+/- 43.4) and 33.7 (+/- 5.68) mg x kg body weight(-0.75) x d(-1), respectively, were obtained using the regression technique. The differences in results between the two techniques were not statistically significant. Daily excretions of creatinine nitrogen were not significantly (P = 0.64) different between the protein-free and regression technique (mean +/- SEM, 14.4 +/- 0.49 and 15.9 +/- 1.05 mg/kg body weight(0.75), respectively). The endogenous urinary total and urea nitrogen excretion of adult domestic cats is higher than values for other mammals such as humans, dogs, rats and pigs.