Portal de Periódicos da CAPES

Tannin Chemistry in Relation to Digestion

1992; University of Arizona; Volume: 45; Issue: 1 Linguagem: Inglês

10.2307/4002526

2162-2728

Ann Hagerman, Charles T. Robbins, Yohan. Weerasuriya, Thomas C. Wilson, Clare McArthur,

Nitrogen and Sulfur Effects on Brassica

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-defhred 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.Tannins are a chemically diverse group of water soluble phenolits which bind proteins to form soluble or insoluble complexes (Bate-Smith and Swain 1962, Hagerman 1989).Tannins are widespread among dicotyledenous forbs, shrubs, and trees (Haslam 1979) and are thus ingested by many herbivorous mammals.Dietary tannin diminishes protein and dry matter digestibility in some mammals (Robbins et al. 1987a(Robbins et al. , 1987b) ) but does not decrease digestion in others (Driedger and Hatfield 1972).Tannin sometimes acts as a toxin rather than a digestion inhibitor (Mehansho et al. 1987a).The diversity of effects of tannin on digestion is due in part to differences in the physiological capabilities of animals to handle tannins and in part to differences in the chemical reactivity of various types of tannins.Recent work has demonstrated that several mechanisms are used by animals to counteract the effects of ingested tannins on digestibility.For example, tannin has little effect on digestibility in