We studied the effect of quercetin on antioxidation in laying hens in vivo and in vitro. In vitro, the effect of quercetin on antioxidation was researched using three methods, including radical scavenging, protection of biological macromolecules and reducing power, and vitamin C was used as a positive control. To investigate the effect of quercetin on antioxidation, performance and the optimum dosage of quercetin for improving laying rate in vivo, 240 of 37-week-old healthy Hessian laying hens with the simi...