Effect of Dietary Protein Intake on Creatinine Excretion and the Creatinine-Nitrogen Ratio in Bovine Urine

The effects of varying nitrogen intake and the relationship of diurnal variation to creatinine excretion and to the creatinine-nitrogen ratio in bovine urine were studied. Treatment levels were 8.9, 11.3 and 14.2% crude protein grain mixtures, fed according to N.R.C. energy requirements, with constant amounts of alfalfa hay and corn silage. Diurnal variation was measured for 24 hr. (at 4-hr, intervals) during three experimental periods. Creatinine and nitrogen concentrations and their ratio were significantly affected by both level of nitrogen intake and diurnal variation. Nitrogen intake was reflected (according to amount consumed) in the magnitude of creatinine and nitrogen concentrations. Midday time periods resulted in highest and middle of the night time periods in the lowest concentrations of creatinine and nitrogen. Creatinine-nitrogen ratios based on concentration closely followed treatment levels and diurnal variations. Urine volume varied significantly during the 24-hr, periods and was inversely related to creatinine and nitrogen concentration. Total urinary creatinine and nitrogen, urine, and the creatinine coefficient were not significantly affected by treatment, period, or by their interaction.