Effect of dietary vitamin E on growth, tissue lipid peroxidation, and liver glutathione level of juvenile hybrid tilapia, Oreochromis niloticus x O. aureus, fed oxidized oil

A feeding experiment was conducted to evaluate the effects of dietary vitamin E levels on growth, tissue lipid peroxidation, and liver glutathione level of juvenile hybrid tilapia fed diets containing oxidized oil. Juvenile hybrid tilapia were fed diets containing 0 to 300 M vitamin E/kg at 12% dietary lipids for 14 weeks. Dietary lipid source (menhaden fish oil/soybean oil) was oxidized to peroxide value (POV) of 98 meq/kg oil. Growth performance of fish fed diets containing 0 and 40 M vitamin E/kg was significantly lower than those fed higher vitamin E (>80 IU/kg) diets. Feed conversion ratio and protein efficiency ratio followed similar trends as growth performance. Further, ascorbate-induced lipid peroxidation in muscle and liver of fish fed diets containing 0 and 40 IU vitamin E/kg was significantly greater than those fed diets containing higher vitamin E (>80 IU/kg). Tissue vitamin E and liver glutathione level increased when dietary vitamin E increased. When weight gain was used as the indicator, using broken-line regression model, dietary vitamin E requirement of juvenile hybrid tilapia fed oxidized oil was 62.5 IU/kg. This value is similar to the dietary vitamin E requirement determined previously for the same species fed un-oxidized oil. (C) 2004 Elsevier B.V. All rights reserved.