Effect of dietary vitamin E on the growth performance and nonspecific immunity in sub-adult turbot (Scophthalmus maximus)

• The dietary requirement of vitamin E was investigated in sub-adult turbot.
• Growth and nonspecific immunological parameters were tested among vitamin E diet.
• Expression of immune-related genes were evaluated among vitamin E diet.

This study investigated the growth performance and non-specific immunity in sub-adult turbot fed with graded levels of vitamin E (0, 120, 240, 480 and 960 mg kg−1) for 15 weeks. Results showed that the final weight, specific growth rate, nitro blue tetrazolium positive leucocytes of head kidney, phagocytic index, serum lysozyme activity and superoxide dismutase activity significantly increased with increasing vitamin E levels. The highest values were recorded in the diet with 480 mg kg−1 vitamin E. However, no significant differences in the hepatosomatic index, viscerosomatic index and survival rate were found among all dietary treatment. Furthermore, the expression levels of complement component 3 (C3), tumor necrosis factor-α (TNF-α) and interleukine 1β (IL-1β) were significantly upregulated in the fish feed with the vitamin E-supplemented diets. Compared with the basal diet, the diet supplemented with 480 mg kg−1 vitamin E significantly augmented the mRNA expression of IL-1β, TNF-α in the spleen and head-kidney, C3 in the liver, respectively. In conclusion, the obtained results indicate the basal diet supplemented with moderate dietary vitamin E (480 mg kg−1) increased the growth, nonspecific immune responses, and expression levels of some immune-related genes in sub-adult turbot. These observations suggest that optimal dietary vitamin E can promote the growth, maintain the health and improve the broodstock management for turbot.