Elevated concentrations of T‐2 toxin cause oxidative stress in the rainbow trout (Oncorhynchus mykiss)

T‐2 toxin is a mycotoxin produced by several Fusarium fungi that can contaminate plant components used in feed for aquaculture. The aim of this 28‐day study was to investigate the effect of the T‐2 toxin in feed in concentrations 1.0 and 1.8 mg/kg (0.01 mg/kg b.w. and 0.018 mg/kg b.w.) on the oxidative stress markers and on the detoxifying enzymes of the rainbow trout. The results showed that T‐2 toxin in both tested concentrations induced oxidative stress and antioxidant defence in the liver of trout manifesting by the increase in activities of enzymes glutathione‐S‐transferase, glutathione reductase and glutathione peroxidase and the decrease in the catalase activity. The increase in lipid peroxidation was recorded only in the higher concentration of T‐2 toxin. Ceruloplasmin activity in the plasma increased at both tested concentrations, and the ferric reducing ability of the plasma increased at the higher toxin concentration. The T‐2 toxin in feed caused alteration of the total protein, albumin and triacylglycerols as well as the alkaline phosphatase activity in the plasma. Despite no changes in histological examination were found, the influence of T‐2 toxin on scavenger system may result in increased sensitivity to other stress factors.