The Utilization of Ammonia-Nitrogen by the Sheep

Ammonia plays a central role in the nitrogen metabolism of the rumen; essentially, this is due, on the one hand, to its origin from the deamination of proteins and other nitrogenous substances and from the hydrolysis of urea, and on the other hand to its use by ruminal bacteria as a source of nitrogen for growth. Ammonia is absorbed from the rumen and converted in the liver to urea, which in part return’s to the rumen in saliva and by direct diffusion from the blood. These events and their implications in the nutrition of the sheep are reviewed, and attention is drawn to some deficiencies in present knowledge of this important aspect of ruminant metabolism.