Effects of vitamin E on growth performance and antioxidant status in juvenile grass carp Ctenopharyngodon idellus

• Dietary vitamin E requirement of juvenile grass carp was determined.
• Vitamin E improves the antioxidant capacity of liver and serum in grass carp.
• Excess vitamin E levels might decrease growth and inhibit the AKP activity.

An 8-week feeding trial was conducted to investigate the effects of dietary vitamin E on growth performance and antioxidant status of juvenile grass carp. Semi-purified diets containing six levels of all-rac-α-tocopheryl acetate (0, 25, 50, 100, 200, 400 mg kg− 1) were assayed in triplicate. Growth performance, body composition, antioxidant activity and serum biochemistry parameter were determined. The maximum weight gain (WG), specific growth ratio (SGR) and feed intake (FI) were achieved in fish fed on a diet supplemented with 100 mg kg− 1 vitamin E. Vitamin E supplementation appeared to improve hepatic glutathione peroxidase (GPx) activity significantly, and higher activity of hepatic superoxide dismutase (SOD) was displayed in diets with excess vitamin E. However, serum SOD and catalase (CAT) activity were enhanced in grass carp fed 50 mg vitamin E kg− 1 diet, and then decreased significantly as the content of vitamin E in the diet increased. A consistent decline in the hepatic and serum malondialdehyde (MDA) content was observed in fish fed diets with the increased supplementation of vitamin E. In addition, with the increasing level of vitamin E, serum alanine aminotransferase (ALT) was reduced. Serum alkaline phosphatase (AKP) activity was enhanced in fish fed 50 and 100 mg vitamin E kg− 1 diet, whereas it decreased as the content of vitamin E in the diet increased. Based on the broken-line regression analysis of WG, 100.36 mg kg− 1 vitamin E was the optimal requirement of juvenile grass carp. The benefits of excess vitamin E levels need to be weighed carefully: on the one hand might enhance the antioxidant capacity, on the other hand might decrease growth.