Evaluation of Feed Efficiency in Modulating Cytokine Expression (TNF-α and IL-6) to Reduce Mortality Rate in the Nile Tilapia During Pathogen Challenge Testing

This study aims to evaluate the immunomodulatory effect of varying levels of black soldier fly (BSF) larvae meal substitution in tilapia (Oreochromis niloticus) feed on cytokine gene expression (TNF-α and IL-6) and survival rate during bacterial challenge with Aeromonas hydrophila. A completely randomized design was used, with four treatment groups: control (0% BSF), R-25 (25% BSF), R-50 (50% BSF), and R-75 (75% BSF). Fish were fed formulated diets for 62 days, with feed intake adjusted weekly. Immune parameters, including cytokine gene expression, were analyzed via reverse transcription quantitative PCR (RT-qPCR) in tissues (kidney and spleen). Post-feeding, fish underwent challenge testing with A. hydrophila, and mortality was monitored over seven days. Results indicated that high BSF substitution (R-75) significantly upregulated TNF-α and IL-6 gene expression in both tissues (P<0.05), with the highest levels observed in R-75 compared to other groups. Additionally, fish in R-75 showed enhanced innate immune responses, including increased phagocytosis and respiratory burst activity. Survival analysis revealed that R-75 had the highest survival rate (90%) and the lowest mortality (10%) post-challenge, significantly outperforming lower substitution groups and control. Despite a slight decrease in feed conversion ratio in high BSF groups, the immune benefits and enhanced disease resistance underscore BSF's potential as a sustainable immunostimulant. These findings suggest that 75% BSF larvae meal substitution effectively activates systemic immune responses and improves tilapia resilience against bacterial infections, supporting their use as an alternative to antibiotics in aquaculture feed formulations.