Abstract: To study the oxidative damage and the antioxidant status and mechanisms of them in cows with varying degrees endometritis. The content of nitric oxide(NO), malonaldehyde（MDA）and the activity of superoxide dismutase（SOD）, glutathione peroxidase（GSH-Px) in serum and uterine secretions of endometritis cows were detected. The total white blood cells and percent of PMN in CE and SE were significantly higher than the control（P＜0.01, P＜0.05）. The content of NO and MDA in serum and uterine secretions of clinical endometritis cows was significantly higher than the control (P＜0.01)，but subclinical endometritis was not different, and the activity of SOD and GSH-Px with clinical endometritis was significantly lower than control group （P＜0.01,P＜0.05）. It could be concluded that the increasing of free radicals and lipid peroxide and the imbalance of antioxidant defense system in serum and uterine secretions of endometritis cows was one reason of cytopathological damage in uterine tissue.

Key words: Holstein cow; endometritis; oxidative damage; antioxidant capability