Effect of dietary vitamin E and selenium on growth, survival and the prevalence of Renibacterium salmoninarum infection in chinook salmon (Oncorhynchus tshawytscha)

Groups of juvenile spring chinook salmon naturally infected with Renibacterium salmoninarum, the causative agent of bacterial kidney disease, were fed diets containing different levels of vitamin E and selenium for 214 days in fresh water and 110 days in seawater. The fish were fed vitamin E at concentrations of either 53±3 mg (designated e) or 299±9 mg (designated E) α-tocopheryl acetate equivalence/kg dry diet in combination with sodium selenite to give selenium concentrations of either 0.038±0.008 mg (designated s) or 2.49±0.15 mg (designated S)/kg dry diet. No mortality occurred in the group fed the diet, whereas mortality was 3% in the groups fed the and diets, and 31% in the group fed the diet. At the end of the experiment, weight gain and hematocrit values were significantly greater in those fish fed the E diets compared with those fed the e diets, whereas the hepato-somatic index was significantly higher in fish fed the e diets. Glutathione peroxidase activity in blood plasma was significantly higher in fish fed the S diets compared with those fed the s diets. No definite effect of dietary vitamin E and selenium on the prevalence and severity of natural R. salmoninarum infections was demonstrated.