Optimal feeding regimes for genetically improved farmed tilapia: ration effects on growth, survival, and water quality

Abstract

The rapid expansion of tilapia aquaculture necessitates feeding strategies that enhance growth while minimizing environmental impacts. This study investigated the effects of three feeding rations 3%, 8%, and 12% of body weight per day on growth performance, feed utilization, survival, and water quality in Genetically Improved Farmed Tilapia (GIFT) fingerlings cultured in northern Sri Lanka. A total of 3000 fingerlings (initial mean weight: 30.62 ± 0.23 g) were randomly allocated into 12 cement tanks (37 m²; stocking density: 250 fish/tank) in a completely randomized design with four replicates per treatment. Fish were fed a commercial diet (30% crude protein) thrice daily over 56 days. Weekly measurements included growth parameters, feed conversion ratio (FCR), survival, and key water quality indicators. Significant differences (p <0.05) were observed in growth and FCR across treatments. The 8% ration produced the highest performance, with a final mean weight of 338.07 ± 12.4 g and length of 28.01 ± 0.8 cm, outperforming both the 3% (146.60 ± 8.2 g; 16.38 ± 0.5 cm) and 12% (332.27 ± 10.6 g; 27.85 ± 0.7 cm) rations. While the 3% ration had the best FCR (0.25 ± 0.02), its low growth made it economically unviable. The 8% ration achieved a balanced outcome (FCR: 0.43 ± 0.03). Survival rates were high (92–96%) with no significant variation among treatments. Water quality remained within acceptable limits, although higher rations elevated total ammonia nitrogen and total dissolved solids significantly (p <0.01). Overall, feeding GIFT fingerlings at 8% body weight/day offers optimal growth and efficiency without compromising water quality or survival. These findings support sustainable intensification of tilapia culture, particularly in resource-limited tropical regions. Further research should assess economic feasibility in larger-scale production systems.