The aim of the study was to evaluate the stress response and the oxidant/ antioxidant equilibrium against shearing process in sheep. Blood malon-dialdehyde (MDA) and glutathione (GSH) concentrations, plasma cortisol, glucose and cholesterol concentrations as well as plasma total antioxidant activity (AOA) were measured in 18 female Chios sheep one hour before a traditional shearing procedure and immediately after. Circulating MDA and cortisol concentrations were dramatically increased compared to initial values after shearing whereas GSH concentrations were significantly depressed. The variations of the other biochemical parameters were not significant. These results demonstrate that MDA and GSH are the most powerful markers for evaluating the oxidant/antioxidant status and that shearing was a stressful situation leading to an oxidative stress which can be amplified by strong glucocorticoid secretion
