Effect of grape pomace concentrate and vitamin E on digestibility of polyphenols and antioxidant activity in chickens

Grape pomace provides a rich source of polyphenols that have the capacity to act as powerful antioxidants. An experiment was conducted to study the effect of inclusion of grape pomace concentrate (GPC) at levels of 15, 30, and 60 g/kg and alpha-tocopheryl acetate (200 mg/kg) in broiler chicks (21 to 42 d of age) on performance; digestive organ sizes; protein; fat; hydrolyzable polyphenol and condensed tannin digestibilities; the antioxidant activity of diet, serum, ileal content, and excreta; and the susceptibility to oxidation of breast meat during refrigerated storage. The inclusion of GPC did not affect the performance; the apparent ileal digestibility of CP; the relative abdominal fat, liver, pancreas, and spleen weight; and the relative intestinal length. Fat digestibility was reduced in birds fed control and GPC diets compared with birds fed vitamin E. Ileal and fecal digestibility of hydrolyzable polyphenols and condensed tannins reached values in a range of 56 to 73% and 14 to 47%, respectively. The GPC diets reduced ileal and fecal digestibility of hydrolyzable polyphenols. Antioxidant activity in GPC diet, ileal content, and excreta [ 2, 2-azinobis (3ethilenzotiazolin)-6-sulfonate method] and GPC diet (ferric antioxidant power method) exhibited higher scavenging free radical capacity than control and vitamin E diets. The lipid oxidation in breast meat was lower in the birds fed the supplemented vitamin E diet than the control diet after 1, 4, and 7 d of refrigerated storage. Oxidative stability in breast meat at 1, 4, and 7 d of storage was equivalent in GPC diets compared with the vitamin E diet. In conclusion, the inclusion of GPC (up to 60 g/kg) did not impair chicken growth performance, digestive organ sizes, and protein digestibility. Hydrolyzable polyphenols were more bioavailable than condensed tannins. Antioxidant activity in diet, excreta, ileal content, and breast muscle were increased in GPC diets. The GPC supplementation was equally as effective in antioxidant potential as vitamin E. On the basis of these observations, we concluded that GPC could be a new source of antioxidant in animal nutrition.