Dietary Vitamin C Fortification Enhances the Growth Performance, Hematological Status, Defensive Antioxidant Enzymes, and Resistance Against Aeromonas Hydrophila Infection for Bullseye Snakehead (Channa marulius)

To evaluate the impact of increased dietary Vitamin C (VC) levels on the survival, growth performance, hematological serum biochemistry, immune system response, antioxidant enzyme activity, stress parameters, and susceptibility of bullseye snakehead (Channa marulius) to Aeromonas hydrophila infection, a 90-day feeding trial was conducted. Four (40% crude protein) isonitrogenous diets with 0 (basal diet), 75, 150, and 300 mg/kg of targeted diet VC were prepared, having analysed VC contents of 4.6, 67.3, 142.5, and 275.8 mg/kg, respectively. At the end of the trial, results showed significant improvements in weight gain % (104.33±6.0 g fish−1), lowest feed conversion ratio (1.67±0.04), and specific growth rate %/day (1.93±0.06) with added VC. Hematological parameters improved dose-dependently, with significant increases in total cholesterol, total protein, and triglycerides, and alanine phosphatase activity at 275.8 mg/kg of VC. Alanine aminotransferase and aspartate aminotransferase activities decreased, suggesting improved liver integrity. Serum electrolyte levels and antioxidant enzymes rose with higher VC incorporation, while serum cortisol and glucose levels dropped, suggesting reduced stress. Liver VC content also increased dose-dependently. Fish on VC fortified diets showed higher survival rates against A. hydrophila challenge. The ideal VC requirement for liver content and weight gain (%) is estimated between 230 and 273 mg/kg based on third-order polynomial (cubic) regression analysis.