Re-evaluation of the vitamin E requirements of juvenile tilapia (Oreochromis niloticus X O-aureus)

A 10-week feeding trial was conducted to re-evaluate the level of dietary v itamin E (DL-alpha -tocopheryl acetate) that mas adequate for juvenile tila pia Oreochromis niloticus XO. aureus given diets containing two dietary lip id concentrations. Purified diets with eight levels of vitamin E (0, 25, 50 , 75, 100, 150, 200, 400 mg/kg diet) at either 50 or 120 g lipid per kg wer e each given to three replicate groups of tilapia (mean weight: 0.69 (s.e. 0.02) g) reared in a closed, recirculating system. Food efficiency and prot ein deposition were significantly (P < 0 05) higher in fish given 50 mg vit amin E per kg diet and 75 mg/kg diet in the 50 and 120 g lipid per kg group s respectively, compared with fish given the unsupplemented control diet. M ortality of fish was not affected by dietary treatment. Weight gain and liv er microsomal ascorbic acid-stimulated lipid peroxidation data analysed by broken-line regression indicated that tile optimum dietary vitamin E requir ements in juvenile tilapia are 42 to 44 mg vitamin E per kg and 50 to 66 mg vitamin E per kg in 50 and 120 g lipid per kg diets, respectively.