EN
This paper presents the results of an experiment aimed to determine the activity of selected antioxidant enzymes: superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), conducted on 24 Hy-Line Brown layers raised in a battery cage system. The hens were divided into two groups, non-infested and infested with Dermanyssus gallinae. It was found that the exposure to the infestation significantly increased SOD and GPx activity and decreased CAT activity. Changes in the activity of the investigated enzymes may indicate the occurrence of oxidative stress in consequence of long-term infestation with the parasite.