Impact of condensed tannin containing legumes on ruminal fermentation, nutrition and performance in ruminants: a review

Legume forages, such as sainfoin, and birdsfoot trefoil can increase the forage quality and quantity of western Canadian pastures, thus increasing producer profitability due to increased gains in grazing ruminants, while reducing risk of bloat in legume pastures due to the presence of proanthocyanidins. Proanthocyanidins or condensed tannins (CT) are secondary plant polyphenol compounds that have been regarded as anti-nutritional due to their ability to bind protein in feeds, enzymes, and microbial cells, therefore disrupting microbial digestion and slowing ruminal protein and dry matter digestion. Research has shown that at high concentrations (>50 g kg-1 DM), CT can disrupt microbial digestion. However, at low dietary inclusion rates (5-10 g kg-1 DM) they reduce bloat risk, and increase ruminal undegradable protein (RUP), reduce enteric methane production, and confer anthelmintic activity. Yet, research gaps still exist regarding grazing persistence and forage yield of novel CT containing forages and their biological activity due to their vast differences in CT stereochemistry, polymer size, and intermolecular linkages. The objectives of this review are to summarize information regarding the impact of CT on ruminal fermentation, carbohydrate and protein metabolism, and the potential to identify and select for forages that contain condensed tannins for ruminant production.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author