The effects of long-term dietary administration of corticosterone (CORT) on the induction of oxidative injury in broiler chickens (Gallus gallus domesticus) were evaluated. The experimental broiler chickens were fed with a diet supplemented with 30 mg CORT/kg diet for 2 weeks from 14 days of age onwards, while control chickens continued to consume the control diet. The growth performance parameters were recorded weekly, and a blood sample was obtained from eight birds of both groups before CORT administration and at 3, 7 and 14 days after treatment. The results showed that chronic CORT administration resulted in enhanced proteolysis and gluconeogenesis. Furthermore, CORT administration may initially induce the formation of reactive oxygen species (ROS) as indirectly reflected by an increase in lipid peroxidation. However, the significantly increased plasma uric acid (UA) and ceruloplasmin (CP) levels after 3 days of treatment indicates an enhancement of the nonenzymatic antioxidant capacity during stress, and in this way, the development of a more severe oxidative injury is alleviated. Broiler chickens seem to adapt to high circulating CORT levels in terms of their redox homeostasis after 3 days of treatment under the present experimental conditions. (C) 2004 Elsevier Inc. All rights reserved.