Effects of dietary tocotrienol on growth, digestive enzyme activities, antioxidant capacity, histology, and disease resistance of Largemouth Bass fingerlings

Abstract

ObjectiveWe sought to assess the efficacy of feeding tocotrienol, a member of the vitamin E family, as it impacts physiological functions in fingerling fish.MethodsFingerling Largemouth Bass Micropterus nigricans with an initial mean body weight (±SD) of 0.98 ± 0.09 g were fed five diets containing tocotrienol at 0, 10, 20, 30, and 40 mg/kg (T0, T10, T20, T30, and T40 diets, respectively) for 42 days. After the feeding experiment, fish were challenged with Largemouth Bass ranavirus (LMBV) and monitored for 48 h.ResultFindings indicated a positive impact of tocotrienol‐supplemented diets on fingerling survival. Furthermore, the weight gain and specific growth rate of fish that received the T30 and T40 diets were significantly higher than those of fish that were fed the T0 diet. Tocotrienol supplementation improved the protein efficiency ratio and condition factor and increased the whole‐body lipid and protein content. Conversely, the hepatosomatic index, viscerosomatic index, and feed conversion ratio were significantly decreased by tocotrienol supplementation. Fish that were fed the T30 and T40 diets exhibited significantly higher hepatopancreas lipase activity and intestinal protease activity. Generally, superoxide dismutase and catalase activities in the liver increased as the tocotrienol level increased. Additionally, the liver malondialdehyde concentration decreased, and there was an improvement in the structure of liver cell tissue. Survival at 48 h after the LMBV challenge was significantly higher in fish that were fed the T30 and T40 diets compared to fish that were given the T0 diet. Maximum specific growth rate was observed at a tocotrienol concentration of 33.63 mg/kg.ConclusionResults suggest that supplementation of Largemouth Bass fingerling diets with appropriate quantities of tocotrienol can enhance survival, growth, antioxidant capacity, digestion, and uptake of nutrients as well as disease resistance.