Dietary vitamin E effects on growth, fillet textural parameters, and antioxidant capacity of genetically improved farmed tilapia (GIFT), Oreochromis niloticus

An 8-week feeding trial was carried out to assess the effects of dietary vitamin E on growth, fillet texture, and antioxidant capacity of genetically improved farmed tilapia (GIFT), Oreochromis niloticus. In total, 240 fish (initial body weight 79.37 g) were assigned to four triplicate groups (20 fish per replicate) and fed diets supplemented with one of the four vitamin E (dl-alpha-tocopheryl acetate) concentrations: 0 (control diet), 40, 200, and 1000 mg kg(-1). Fish fed the control diet had significantly poorer growth (weight gain; 185.29 vs 214.25-219.28%), feed efficiency (63.99 vs 70.44-72.30%), and survival rate (86.67 vs 95-100%) than those fed vitamin E-supplemented diets (P < 0.05). Protein percentage in muscle of the fish fed the 40 mg kg(-1) diet was significantly higher than that of the control group (19.95 vs 18.65%) (P < 0.05). Based on texture profile analysis, fish in the control group had significantly lower cohesiveness (0.43 vs 0.47-0.50), resilience (0.25 vs 0.28-0.31), and chewiness (340.8 vs 406.4-504.5 g) than fish in the other groups (P < 0.05). Vitamin E supplementation significantly enhanced superoxide dismutase activity in serum and muscle and catalase activity in serum (P < 0.05). Malondialdehyde contents in serum and muscle significantly decreased (P < 0.05). These results suggest that no less than 40 mg kg(-1) vitamin E improve growth performance, fillet flesh quality, and antioxidant capacity of GIFT. On the basis of second-order polynomial regression, the optimum vitamin E supplemented level for GIFT is about 573.8-582.3 and 655-752.5 mg kg(-1) based on fillet texture and serum antioxidant capacity, respectively.