Effect of Dietary Papaya (Carica papaya) Leaf Meal on Growth Performance and Haematological Responses of Nile Tilapia (Oreochromis niloticus) Fingerlings Reared in a Recirculating Aquaculture System.

In the pursuit of sustainable aquaculture, the integration of unconventional plant-based feed additives like papaya leaf meal (PLM) offers a promising approach for enhancing fish growth while reducing feed costs and environmental impact. To evaluate the efficacy of PLM as a growth promoter, four experimental diets were formulated by gradually incorporating PLM at inclusion levels of 0%, 3%, 6% and 9%. Nile tilapia fingerlings were cultured over a 60-day period within a recirculating aquaculture system comprising 12 tanks, with three replicates assigned to each treatment group. Fish were fed twice daily at a rate corresponding to 3% of their body weight. The diet with the highest inclusion of PLM (9%) resulted in significantly (p < 0.05) improved mean weight gain (11.44 g), per cent weight gain (82.67%), specific growth rate (SGR) (1.06%/day), feed conversion ratio (2.23), feed conversion efficiency (0.44), protein efficiency ratio (1.28) and overall fish yield (2.04 kg/m3/60 days) when compared to the control, 3% and 6% PLM-based diet. Furthermore, the length-weight relationship in all dietary treatments indicated a positive allometric growth pattern in Nile tilapia fingerlings. A notable improvement in haematological parameters, red blood cells (3.10 ± 0.95 × 106/mm3), white blood cells (132.98 ± 2.26 × 103/mm3) and haemoglobin (12.15 ± 0.68 g/dL) was observed in treatment having 9% PLM with statistically significant differences among the treatments (p < 0.05). Therefore, these findings indicate that PLM inclusion up to 9% in diet is non-toxic and positively impacts growth performance, making it a viable growth enhancer in tilapia fingerling diets.