Feeding dry stevia leaf (Stevia rebaudiana) or xylanase improves the hepatic antioxidative status of broiler chickens.

Four diets, formulated with and without stevia and with and without exogenous xylanase, following a 2 × 2 factorial design, were prepared. Each diet was fed ad libitum to birds in eight pens (three birds in each pen) in a randomised block design. It was found that birds fed xylanase grew faster, used the feed more efficiently and had an increased concentration of hepatic α-tocopherol and vitamin E concentrations (P < 0.05). Feeding stevia did not affect growth performance (P > 0.05), but increased hepatic CoQ (P = 0.05), lutein, zeaxanthin and total carotenoids (P < 0.001) concentrations. There were no dietary stevia by xylanase interactions (P > 0.05) for any of the studied variables. The results showed that alone, dietary stevia and dietary xylanase can improve the antioxidative status of birds through enhancing dietary antioxidant availability.