Condensed Tannins Attributes: Potential Solution to Fescue Toxicosis?

Tall fescue (Schedonorus arundinaceous (Schreb.) Dumort. nom. cons. Lolium arundinaceum (Schreb.) Darbysh.) toxicosis results from the consumption of alkaloids released by wild-type endophytes (Epichloe coenophiala) that live in symbiosis with the plant. Alkaloid consumption causes significant production and reproductive losses which cost the U.S. beef industry approximately $2 billion every year. Incorporating species that contain condensed tannins (CTs) into forage systems may be an effective strategy to reduce the effects of fescue toxicosis in livestock. It has been hypothesized that stable complexes formed between CTs and toxic alkaloids could help reduce their absorption through the gastrointestinal epithelia, thus reducing their toxic effects. However, it is not yet clear whether CTs are effective in reducing the effects of fescue toxicosis in grazing systems. A comprehensive literature search was carried out using Google Scholar to identify studies relevant to the research question, from which the cited articles were selected. This review covers the value and issues of tall fescue employed as useful forage, summarizes the impact endophyte-infected tall fescue can have on cattle, and sets out the current management strategies implemented to minimize fescue toxicosis. The review continues with a brief summary of tannin structure and the well-documented benefits that CT-containing forages can contribute to the productivity and sustainability of ruminant agriculture. Finally, a summary of the potential forage sources, mechanisms, and benefits of CTs in reducing the negative post-ingestion effects of fescue alkaloids in livestock is provided.