Influence of dietary enzyme addition on polyphenol utilization and meat lipid oxidation of chicks fed grape pomace

Grape pomace provides a rich source of polyphenols that have the capacity to act as powerful antioxidant. An experiment with ten dietary treatments (30 birds/treatment), was conducted to study the effect of inclusion of phenolic compounds from grape pomace (GP) added at different levels (0, 5, and 10%) and the addition (individually or combined) of hydrolyzing enzymes (carbohydrase enzyme complex and tannase at 500ppm) in broiler chicks (1 to 21days of age). A diet supplemented with 200ppm of α-tocopheryl acetate (αT) was also used. Growth performance, ileal and fecal total polyphenol content, thigh meat lipid oxidation, and α-tocopherol and fatty acid content of thigh meat were determined. No differences were observed in body weight, feed consumption and feed efficiency among the different treatments. Birds fed GP diets showed a higher ileal and fecal polyphenol content. The inclusion of tannase in GP diets increased ileal polyphenol content and did not affect the fecal polyphenol content. Oxidative stability of thigh meat after 1 and 4days of refrigerated storage increased with dietary addition of αT and GP, and was worsened when GP was supplemented with carbohydrases. Meat α-tocopherol content was increased by dietary addition of αT. Birds fed αT and GP diets showed higher meat polyunsaturated fatty acid content, while monounsaturated fatty acid was reduced. The addition of tannase to GP diets reversed the beneficial effect observed on fatty acid content obtained in GP diets. In conclusion, dietary GP reached the protective effect of α-tocopherol by reducing the susceptibility of meat to lipid oxidation and increasing the PUFA content. The inclusion of tannase in diets containing GP increased the amount of total polyphenol released in the intestine, but did not improve the stability to meat lipid oxidation.