Immunostimulatory Effect of Betal Leaf Extract on Labeo catla and its Resistance Against Aeromonas hydrophila

Aquaculture plays a vital role in global fish production, but rising antibiotic resistance threatens the sustainability of this industry. This study explores the potential of betel leaf extract as a natural immunostimulant to improve fish health. The present experiment investigated the immunostimulatory effect of betel leaf extract on Labeo catla and its resistance against Aeromonas hydrophila. The experiment was conducted in 2024 at the Department of Aquaculture, College of Fisheries Science, Kamdhenu University, Veraval. It was conducted in rectangular plastic tanks using a Completely Randomized Design (CRD) with five treatments and four replications. T1, T2, T3, and T4 diets were prepared by incorporating betel leaf extract at 0.2%, 0.4%, 0.6%, and 0.8%, respectively, while T0 served as the control. The extract was directly supplemented into the feed and processed into feed to ensure uniform distribution. Fish were fed at 6% of their body weight twice daily for 45 days. Key parameters such as specific growth rate (SGR), feed conversion ratio (FCR), total erythrocyte count (TEC), total leucocyte count (TLC), respiratory burst activity, and disease resistance were assessed. The highest performance was observed in T4, which recorded an SGR of 1.49 ± 0.008, an FCR of 1.99 ± 0.02, and a survival rate of 93.33 ± 1.66% (P < 0.05). Immunological parameters were also significantly improved in T4, with TEC at 1.695 ± 0.006 cells/mm³ and TLC at 28.2 ± 0.06 cells/mm³ (P < 0.05). A challenge study against A. hydrophila confirmed that T4 exhibited the highest survival rate (93.33%). These findings suggest that incorporating betel leaf extract at 0.8% in fish feed enhances growth, immune response, and disease resistance, making it a viable natural alternative to antibiotics for sustainable aquaculture.