Legumes, some fruits and vegetables, tea, chocolate, wine, coffee, vinegar.
Tannin-binding salivary proteins. Partially by soaking and cooking. About 90% by germination.

Zinc and iron deficiency, decrease in both growth rate and body weight gain, perturbation of mineral absorption, inhibition of digestive enzymes, accelerate blood clotting, produce liver necrosis.

Tannins are water soluble phenolic compounds with a molecular weight greater than 500 daltons. They have the ability to precipitate proteins from aqueous solution. There are two different groups tannins:- hydrolyzable tannins and condensed tannins. Condensed tannins are widely distributed leguminous forages and seeds. Cattle and sheep sensitive to condensed tannins, while goats are more resistant (Kumar, 1983; Kumar and Horigome, 1986; Kumar and Vaithiyanathan, 1990; D’Mello, 2000).Tannins may form a less digestive complex with dietary proteins and may bind and inhibit the endogenous protein, such as digestive enzymes (Kumar and Singh, 1984). Tannin-protein complexes involve both hydrogenruminants bonding and hydrophobic interactions. The precipitation of the protein-tannin complex depends upon pH, ionic strength and molecular size of tannins. Both the protein the precipitate increase with increase in molecular size of tannins (Kumar and Horigome, 1986). However, when the molecular weight exceeds 5,000 daltons, the tannins become insoluble and lose their protein precipitating capacity and degree of polymerization becomes imperative to assess the role of tannins in ruminant nutrition (Kumar, 1983; Lowry, 1990). Tannins have been found to interfere with digestion by displaying anti-trypsin and anti-amylase activity. Helsper et al. (1993) reported that condensed tannins were responsible for the testabloat bound trypsin inhibitor activity of faba beans. Tannins also have the ability to complex with vitamin B (Liener, 1980). Other adverse nutritional effects of tannins have been reported to include intestinal damage, interference with iron absorption and the possibility of tannins producing a carcinogenic effect (Butler, 1989).

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