Adverse Effect of Tannins on Animal Health

Non ruminant are highly susceptible to adverse effect of tannins. As little as 0.5% tannic acid is sufficient to cause growth depression in poultry and 5% tannin can cause 70% mortality (Vohra et al., 1966). A two per cent levels of tannins cause olive green coloration of egg yolk and similar effect found while 0.5% red gum extracted tannins included in the diet of hens (Jaslyn and Glick, 1969). Tannins cause leg abnormalities in chick which is due to defective formation of bone matrix (Armstrong et al., 1974). It is characterized by outward bowing of leg with swelling at hock (Elkin et al., 1978). Tannins produced gastritis and enteritis and it leads to more absorption of tannins into body systems which causes liver and kidney damage. Feeding of diet containing 16 g tannins per kg dry matter induced high mortality in chicken along with atrophy and shortening of villi in the ileal mucosa. Toxic effect of tannins in ruminant is less severe than non ruminant.

However, feeding of tannins at a level 1.56 g per kg body weight cause destruction of intestinal villi, hypertrophy of intestinal submucosa, glands, fatty degeneration of hepatic cell, coudy swelling and hydropic degeneration of urinary tubules (Singh, 1979). Feeding of tannins at the rate of 1.1g per kg body weight to goat produced renal, pancreatic and skin necrosis (Tripathi et al., 1984). Lesions were not seen in sheep even fed with 8g tannic acid per kg body weight, but intraperitoneal administration of 0.1g tannic acid produced liver necrosis (Zhu et al., 1992). Garg et al.,(1992) fed oak leaves (immature) ad lib to cattle which contained 97.7 mg hydrolysable (tannic acid equivalent) and 5.8 mg condensed (catechin equivalent) tannins per g dry leaves, for 2 days and they observed a numbers of abnormal symptoms. Cattle showed anorexia, constipation, depression, respiratory distress, dry muzzle, sub normal body temperature, cessation of rumination, polydiosia, polyurea, voided dark hard and pelleted faeces coated with blood and mucous and also showed brisket edema and finaly die.

Feeding of oak leaves containing 1542 mg tannins (tannic acid equivalent) for 7 days to calves produced renal failure, hematuria, glycosuria and increased blood urea nitrogen (Plumlee et al., 1998). Ulcerative lesions are produced in the gastrointestinal tract of sheep when fed 50g of quabracho tannins per kg diet dry matter (Dawson et al., 1999).

In conclusion, these are few examples of feed resources discussed here but plenty of other feeds are still unexplored yet. Hence, lot of potential for searching feed and make them a palatable feed for the animal feeding.

• Tanniniferous Feeds for Dairy Animals
• Effect of Tannins on Feed Intake and Digestibility of Nutrients
• Beneficial Effect of Tannins on Animal Production