Tanniniferous Feed Resources in Dairy Animals: A Review

Use of unconventional feeds is an alternate source to mitigate the shortage of grains and byproducts. Since various unconventional feeds are produced in huge quantities every year and available comparatively at cheaper rate, therefore, the feed industry has a preference to use these materials in order to have maximum benefit from locally available unconventional feeds. Presence of tannin in diets less than 4 % is however, advantageous to ruminants as it acts as natural protein protectant and thus reduces the degradation of protein by forming tannin protein complex (TPC) in the rumen and subsequently enhances the amino acids availability in lower gut thereby increases the rumen bypass protein. It reduces proteolysis of forage protein in the rumen, reduces rumen and plasma ammonia concentrations, reduces blood plasma concentration and increases the net absorption of essential amino acids especially branched chain amino acids from the small intestine. Tannin containing diet improved milk production and reproduction performance in dairy cows. Tannin is also hydrolyzed in the animal system and releases some antioxidants like catechin, epicatechin, catechin gallate, gallic acid etc., which have therapeutic values. These metabolites have certain properties like anti-carcinogenic, anti-oxidative immuno-stimulatory and enhancer of reproduction performance. Catechin serves as powerful antioxidant against lipid peroxidation when phospholipid bilayers are exposed to aqueous oxygen radicals. The reproductive efficiency of ewes grazed on L.corniculatus increased the effect on cell mediation by the condensed tannin. These metabolic changes may promote events such as folliculogenesis, conception, attachment, embryo survival, foetal growth and lamb viability. The effect of tannins on animals ranges from beneficial to toxicity depending on the type of animals, age of animals, type and level of tannins in the feeds, the biological activity of tannins, level of tannin intake, quality of basal diets etc.