Twenty-four-hour urinary creatinine and urea nitrogen excretion in male white-tailed deer

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Abstract
During 5-d trials in spring and summer we investigated the constancy of creatinine and urea nitrogen excretion and the urea nitrogen:creatinine ratio in 24-h urine samples from 12 male white-tailed deer (Odocoileus virginianus) and the relationship of these metabolites with body mass and dietary nitrogen intake. During both trials, 24-h urinary creatinine excretion remained stable (CV of 13.5 and 18.5% for the spring and summer trials, respectively), and there was no difference between deer fed a high-protein diet and those fed a low-protein diet. However, urinary urea nitrogen excretion and urea nitrogen:creatinine ratios were significantly lower in the latter group. Mean daily creatinine coefficients (0.22–0.27 mmol excreted/kg body mass) were comparable to those in other mammalian species. During both trials, urinary creatinine excretion was significantly related to body mass but not to dietary nitrogen intake. Urea nitrogen excretion and urea nitrogen:creatinine ratios were significantly related to mass-specific nitrogen intake, but not to body mass or 24-h urinary creatinine excretion. Using 24-h urinary creatinine excretion, mean muscle mass of our deer was estimated to be 58 and 57% of whole body mass in the spring and summer trials, respectively.