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

ABSTRACT

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 (~580 g kg⁻¹ crude protein, 120 g kg⁻¹ crude lipid) experimental larval diets with varying levels of vitamin E 0 (control E₀), 100 (E₁₀₀), 200 (E₂₀₀), 300 (E₃₀₀) and 400 (E₄₀₀) 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 (E₂₀₀) 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 E₀ fed diet. Also, fish feed with E₂₀₀ diet had a significantly higher protein efficiency ratio (0.53 ± 0.08) than the control (E₀) (0.40 ± 0.01). Vitamin E and lipid content of postfed whole larvae were linearly correlated (R² = 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_300, and E₄₀₀ were higher, compared to E₀ and E₁₀₀ treatments. Red blood cell (p < 0.05) and white blood cell (p < 0.01) counts were significantly higher in E₂₀₀ treatment than in the rest of the treatments. Larvae fed with an E₂₀₀ and E₃₀₀ 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.

KEYWORDS:

• Larval nutrition
• alpha-tocopherol
• feed supplementation
• production
• aquaculture

Acknowledgments

The authors express sincere gratitude to the Indian Council of Agricultural Research for providing financial support for this research project. The first author is thankful to the Tamil Nadu Dr. J. Jayalalithaa Fisheries University at which he is pursuing a doctoral degree. We also thank the feed mill staff at Muttukadu Experimental Station, ICAR-CIBA, for timely help in conducting the experiment and for laboratory analysis.

Disclosure statement

No potential conflict of interest was reported by the authors.

Data availability statement

The data that support the findings of this study are available from the lead author.

Additional information

Funding

The work was supported by the Indian Council of Agricultural Research [FISHCIBASIL 201800800136].