Effects of Tannins on Poultry Nutrition

One of the most important secondary metabolite found in cereals, legumes, vegetables and fruits is tannins. Tannins are polymeric phenolic compounds in the amorphous structure which are nitrogen-free, hydrolyzed and condensed forms. Tannins that can be hydrolyzed are found in smaller amounts in plants. Condensed tannins have flavonoid units resistant to hydrolysis. Tannins have antioxidant, anticarcinogenic, antimicrobial and antiparasitic functions. On the other hand, due to their anti-nutritional contents, they have some negative effects on poultry. According to ruminants, poultry are more sensitive to tannins. High amounts of tannins lead to performance losses in poultry, such as reduced appetite, reduced feed intake, and poor absorption of nutrients etc. Tannins, also known as potent liver and kidney poisons, cause poultry to develop bone disorders and pathological changes at various levels in tissues, irritation in esophagus, necrosis in crop, gizzard, and duodenum. In this review, the characteristics of tannins, their classification, the general effects of tannins on feeding of poultry and practices that reduce the amount of tannins have been examined.