Microbial interactions with tannins: nutritional consequences for ruminants

Polyphenolics are widely distributed in the plant kingdom and are often pre sent in the diet of herbivores. The two major groups of plant polyphenolic compounds other than lignin are condensed and hydrolysable tannins. These c ompounds can have toxic and/or antinutritional effects on the animal. It is well established that tannins complex with dietary proteins can reduce nit rogen supply to the animal, but the ability of gastrointestinal microorgani sms to metabolise these compounds and their effects on microbial population s have received little attention. In this paper, we review recent literature on the topic as well as present research from our laboratories on the effect of condensed tannins on rumen microbial ecology and rumen metabolism. Interactions of tannins with dietar y components and endogenous protein in the rumen and post-ruminally, and th eir impact on the nutrition of the animal are considered. (C) 2001 Elsevier Science B.V. All rights reserved.