Effect of dietary vitamin E supplementation on growth, fatty acid composition, intestinal histology, and haemato-immune indices of milkfish, Chanos chanos, larvae

Vitamin E is one of the most important vitamins in aquatic animal breeding, larval growth, and development. It is also considered to be a functional feed addtitive for its antioxidant and immunity-improvement role resulting in better survival and growth during early life stages. However, the role of vitamin E in the diet of milkfish larvae has not been studied in detail. Moreover, the optimal requirement of vitamin E for improved survival and growth in the larval stages of milkfish is yet to be ascertained. A 45-day feeding experiment was conducted to elucidate the effect of dietary vitamin E (alpha tocopherol) supplementation on the growth, survival, and fatty acid composition of milkfish, Chanos chanos, larvae. During the trial, five iso-nitrogenous and iso-energetic (similar to 580 g kg(-1) crude protein, 120 g kg(-1) crude lipid) experimental larval diets with varying levels of vitamin E 0 (control E-0), 100 (E-100), 200 (E-200), 300 (E-300) and 400 (E-400) mg kg(-1) were tested in 18 days posthatch larvae (mean weight: 48.25 +/- 0.08 mg). Milkfish larvae (1,500) were randomly distributed into 15 fiber-reinforced plastic (FRP) rectangular tanks of 100 L capacity (n = 100) in a flow-through rearing system. The results revealed that larvae fed with a diet containing vitamin E supplementation at 200 mg (E-200) enhanced (p < .05) the growth performance, final body weight (371.7 +/- 12.80 mg), weight gain percentage (628.76 +/- 63.12%), and specific growth rate (4.31 +/- 0.80%) compared with the E-0 fed diet. Also, fish feed with E-200 diet had a significantly higher protein efficiency ratio (0.53 +/- 0.08) than the control (E-0) (0.40 +/- 0.01). Vitamin E and lipid content of postfed whole larvae were linearly correlated (R-2 = 0.956) with dietary vitamin E inclusions up to 300 mg kg(-1). Histological examinations revealed that the length of intestinal villi and the concentration of lymphoid cells in the lamina propria of the treatments E-200,E- E-300,E- and E-400 were higher, compared to E-0 and E-100 treatments. Red blood cell (p < 0.05) and white blood cell (p < 0.01) counts were significantly higher in E-200 treatment than in the rest of the treatments. Larvae fed with an E-200 and E-300 diet showed significantly (p < 0.05) increased total lymphocyte count, while myelocyte count was significantly decreased (p < 0.01). Based on a curvilinear (polynomial) regression analyses, the optimum specific growth rate, final body weight, weight gain, protein efficiency ratio, and feed efficiency ratio were obtained at dietary vitamin E levels of 210, 205, 207, 243, and 242 mg kg(-1) diet, respectively. Accordingly, the optimum dietary vitamin E required for milkfish in a range of 205 to 243 mg kg(-1) is beneficial for better health, survival, and growth. The findings of this study can be used as the baseline scientific information on the vitamin E requirement for the formulation of a cost-effective diet for milkfish larvae.