The objective of the research was to assess the effects of tannins in ruminant nutrition and the ameliorating effects of polymers.  It also aimed to investigate and propose an improved method for determining concentrations of condensed tannins using the Butanol/HCl assay (Porter et al., 1986). The study has found tannins to suppress microbial growth, carbohydrate degradation and fermentation of mixed rumen microbes and of fungus.