Nitrogen Metabolism in Ruminants: Rate of Ruminal Ammonia Production and Nitrogen Utilization by Ruminants—A Review

Protein is the first limiting nutrient for ruminants grazing indigenous forages during the dry or winter season. As preformed proteins are expensive and in great demand for the feeding of nonruminants, attention of the researcher has turned to the possible use of non-protein nitrogen (NPN) sources for ruminant feeding and to the possible improvement of the utilization of preformed proteins. To obtain maximum utilization of NPN or protein-nitrogen requires knowledge of the metabolism of these compounds by ruminants. This paper is a review of the research work on NPN and protein nitrogen utilization with emphasis upon rates of ammonia production and nitrogen utilization by ruminants.