Nitrogen Metabolism in the Ovine. II. Utilization of Blood Urea and Ammonia1

Abstract

Apparent utilization of infused urea-N was comparable in lambs previously fed a urea-free, high-corn diet to that in lambs previously fed a 3.5% urea diet for several months. Nitrogen balance was improved only slightly by incorporating urea in the diet as compared to infusing it directly into the blood. Lambs receiving urea infusions retained 5.2 gm. (38% of infused urea-N) more per day than control lambs receiving saline infusions. Lambs receiving daily intravenous infusions of 3.3 gm. of ammonia-N as ammonium chloride retained 1.4 gm. more (P<.01) per day than lambs receiving saline infusions. There was a progressive increase in nitrogen balance as the ammonia infusion was extended, but a comparable increase in lambs receiving saline suggested that the “adaptation” was to a poor dietary regime (for example, in terms of N balance) rather than to ammonia per se.