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Animal Nutrition and Feed Technology
Year : 2001, Volume : 1, Issue : 1
First page : ( 3) Last page : ( 18)
Print ISSN : 0972-2963.

Tannins revisited - changing perceptions of their effects on animal system

Singh B*, Bhat T. K.

Regional Station Indian Veterinary Research Institute Palampur - 176 061, India

*Reprint request: Dr. B. Singh, Fax: +91-1894-33063; E-mail: ivriplp@nde.vsnl.net.in.

Abstract

Tannins are a prominent class of compounds which constitute the plant secondary metabolites group. The two major structural groups of tannins are hydrolyzable tannins and condensed tannins. Due to their widespread nature and ability to complex with proteins and other biomolecules, they exert both harmful and beneficial effects on organisms. Hydrolyzable tannins have toxic effect on the animals that feed on forages rich in these tannins. High concentrations of dietary condensed tannins (6–12% DM) depress voluntary feed intake, digestive efficiency and animal productivity. In contrast, forages containing moderate concentrations of condensed tannins (2–4% DM) can exert beneficial effects on protein metabolism in ruminants especially sheep, by slowing degradation of dietary protein to ammonia by rumen microorganisms and increasing protein outflow from the rumen. This results in the increased absorption of amino acids in the small intestine and ultimately leads to increases in lactation, wool growth and live weight gain, without changing voluntary feed intake of the animal. Dietary condensed tannins can also contribute to improved animal health by reducing the detrimental effects of internal parasites in small ruminants and the risk of bloat in cattle. Therefore, forages containing moderate concentrations of condensed tannins can increase sustainability and productivity in intensive grazing systems through increasing the efficiency of animal production, decreasing urinary nitrogen excretion and reducing chemical inputs such as anthelmintics and detergents to control rumen bloat in cattle

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Key words

Hydrolyzable tannins, Condensed tannins, Negative effects, Positive effects.

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