Tannin chemistry in relation to digestion

Abstract

Tannins are a diverse group of compounds which precipitate protein. The impact of tannins on herbivory has been difficult to assess because of diversity in tannin chemistry and in animal physiology. We have evaluated the effects of tannin on large ruminants (deer, sheep) using artificial diets containing well-defined tannins, and have compared the results to those obtained with natural forages. The different effects of condensed tannins and gallotannins on herbivores are related to the chemical stability of the tannins. Commercial tannic acid does not have the same effects on herbivores as gallotannins in natural forages. Molecular weight apparently determines the metabolic fate of gallotannins from various sources.