Nitrogen Metabolism in the Rumen: Microorganisms as a Source of Protein for the Ruminant Animal

Abstract

In the past several years review papers have dealt with a number of different aspects of nitrogen metabolism in the ruminant (McDonald, 1958, 1968; Conrad and Hibbs, 1968; Waldo, 1968; Chalupa, 1968). The present paper is concerned with the qualitative and quantitative evaluation of microbial protein as a source of protein (amino acids) to the host animal. Emphasis has been placed upon those physiological aspects considered to be capable of influencing the amino acid nutrition of the ruminant animal, and especially to some of those systems about which very little specific information is available. Consequently, this paper is an appraisal of several specific aspects of ruminant nitrogen metabolism rather than a review of this subject. The discussion is divided into three general areas (a) a consideration of the amino acid composition and nutritive value of the rumen microorganisms (b) a discussion of factors influencing the availability of the amino acids to the host animal's metabolic system and, finally, (c) a discussion of quantitative aspects of the relative supply of energy and protein to the host animal. Copyright © 1970. American Society of Animal Science. Copyright 1970 by American Society of Animal Science