Effects of dietary vitamin E on hematology, tissue α-tocopherol concentration and non-specific immune responses of Japanese eel, Anguilla japonica

In a 16-week feeding trial, the effects of dietary vitamin E (α-tocopherol, α-Toc) levels on tissue α-Toc concentration, hematology and non-specific immune responses of Japanese eel were examined. Totally five diets were used in this experiment, consisting a basal commercial diet (control) and supplementing 100, 150, 200 or 400 mg α-Toc kg− 1 diet in the form of dl-α-tocopherol acetate. The analyzed α-Toc concentrations of the diets were 32, 112, 158, 212 and 428 mg kg− 1 diet, respectively. For each experimental diet, triplicate groups of fish (initial body weight, 360 g) were fed at a ratio of 2% body weight. At the end of the feeding trial, α-Toc concentration in liver, kidney, muscle and gonad were increased significantly in a dose dependent manner (P < 0.05). Significantly higher hemoglobin and white blood cells count were found in fish fed 212 mg α-Toc kg− 1 diet compared to control. Plasma glucose concentration was decreased significantly in all α-Toc supplemented groups, also significantly higher aspartate aminotransferase and alanine aminotransferase values were obtained at 32 and ≤ 158 mg α-Toc kg− 1 diet compared to the other groups. Significantly higher lysozyme and SOD activities were recorded in fish fed 428 mg α-Toc kg− 1 diet compared to the other groups. The optimal dietary α-Toc requirement was estimated at 212.9 mg α-Toc kg− 1 diet by broken-line regression model based on liver α-Toc concentration.