Symposium on Microbial Digestion in Ruminants: Nitrogen Metabolism in the Rumen

Many excellent reviews and monographs, such as those by Reid (1953), Chalmers and Synge (1954), Annison and Lewis (1961), Barnett and Reid (1961), Lewis (1961) and Preston (1961), are available on the subject of nitrogen metabolism in the rumen. For this reason it is intended that this paper should deal primarily with mechanisms involved in nitrogen metabolism in the ruminant rather than in a complete review of the literature. It is well-established that nitrogen metabolism in the ruminant is dependent upon the complex metabolism of nitrogen compounds by the rumen microbial population. It is also well-established that maintenance of normal microbial activities of the rumen population is dependent upon various associated metabolic activities within the ruminant. In order to consider some of these interrelationships, this paper will not be limited to reactions occurring within the rumen. Nitrogen metabolism, with particular emphasis on the utilization of non-protein nitrogen (NPN), will be considered from the following aspects: Degradation of nitrogenous compounds in the rumen The utilization of NPN by rumen microorganisms Metabolism of absorbed nitrogen