Partition of nitrogen in the urine of African sheep given a variety of low-protein diets

Abstract

1. Sixteen foods, made up with differing proportions of roughage and concentrates and ranging in crude protein content from approximately 2·6% to 10·0%, were each offeredad libitumto Blackhead Persian wether sheep. The nitrogen balance of the sheep and the distribution of nitrogen in the urine were measured.2. Urinary nitrogen excretion decreased with the digestible nitrogen intake. There was a highly significant (P< 0·01) positive correlation between either excretion of urea or of allantoin and digestible nitrogen intake.3. The amount of creatinine excreted varied little with diet but was directly related to the body weight of the sheep.4. For 8 diets, hippurate excretion by the sheep was directly related (P<0·01) to intake of digestible nitrogen, while a significant (P<0·05) positive correlation between the same measures was found for the other 8 diets.5. It is suggested that with certain types of diets the excretion of either nitrogen, urea or allantoin in the urine may be useful indicators of digestible nitrogen intake of low-protein diets by sheep.