Microbial protein supply from the rumen

This paper considers the theory, assessment and prediction of microbial protein synthesis in the rumen. The dif®culties of techniques for assessing microbial protein synthesis, as well as the complexity of the rumen ecosystem, have limited progress. Inconsistencies in the literature undermine the value of incorporating advanced rumen models into rationing schemes and limit the exploitation of microbial protein as an important protein resource for ruminants. The paper gives examples of situations in which particular factors have signi®cant effects on microbial protein synthesis, but moves on to discuss the development of new less-invasive approaches for estimating microbial protein synthesis. The latter approaches have the attraction of offering in-built technology transfer through the development of diagnostic tests, based on samples of milk or urine. Some of these techniques offer a description of rumen function that is less rigorously quantitative (in terms of microbial protein synthesis), but more usefully qualitative (in terms of microbial populations, substrates and interactions). # 2000 Elsevier Science B.V. All rights reserved.