Black soldier fly (Hermetia illucens) larvae oil (BSFL oil) is characterized by a high concentration of saturated fatty acids (SFAs), with lauric acid as the predominant fatty acid (~21% to 50%), which can destabilize bacterial cell membranes. The present study evaluated the effects of a plant-based diet (negative control), a plant-based diet supplemented with 1% BSFL oil, and an animal-based diet, formulated with 13.9% fish meal inclusion (positive control).
The experimental diets (negative control, 1% BSFL Oil, and positive control) were formulated to be isonitrogenous, isolipidic, and isoenergetic, containing 38% crude protein, 6% crude lipid, and 16.2 MJ gross energy/kg. Three hundred and seventy-five hybrid catfish juveniles (average initial weight ~30 g) were equally distributed into fifteen experimental aquaria (110-L, 25 fish/tank, n=5), operating as a recirculating system. Fish received feed rations twice daily, proportional to the tank biomass, which was adjusted biweekly. After 63 days of feeding, fish were weighed and three fish per tank were anesthetized to collect blood, and then euthanized for tissue sampling. The remaining fish from the feeding trial were moved to a flow-through system, and after the acclimation period, fish were subjected to an immersion challenge (3.65 × 106 CFU/mL) using Edwardsiella ictaluri (S97-773), and survival was monitored for 28 days. Hybrid catfish from the positive control group had a higher final weight, biomass gain, feed intake, feed efficiency, and hematocrit percentage (Figure 1). No differences were observed in viscerosomatic index, intraperitoneal fat, hemoglobin, or erythrocyte count. The dietary treatments did not have a significant effect on survival after the bacterial challenge. It can be concluded from the results of this feeding trial that 1% BSFL oil supplementation did not significantly enhance the production performance and health of hybrid catfish fed a plant-based diet. This also highlights the importance of animal proteins in the diets of hybrid catfish juveniles, as the positive control led to significantly better growth parameters.