Optimization of the fish silage-corn bran mixture in the preparation of diets for black soldier flies (Hermetia illucens)

Background: The high cost of conventional protein sources and the environmental impacts resulting from improper management of agro-industrial waste have driven the search for sustainable alternatives for protein production. In this context, Hermetia illucens larvae stand out for their ability to bioconvert organic waste into nutrient-rich biomass. Objective: In this study, the fish silage (FS) of red-bellied Pacu (Piaractus brachypomus) viscera and corn bran (CB) was optimized as a substrate for feeding larvae of H. illucens. Methods: The silage was prepared by controlled fermentation with acidified yogurt, molasses, butylated hydroxytoluene (BHT), and potassium sorbate, while the corn bran underwent aerobic fermentation prior to the formulation of the mixtures. An experimental mixture design was employed, and ANOVA was used to identify the optimal component proportions to maximize larval performance. The zootechnical parameters evaluated included bioconversion (BC), substrate reduction (SR), survival ratio (SB), and feed conversion ratio (FCR). Results: Both FS and CB substrates have significant effects on zootechnical parameters. For SB, it depends linearly on these substrates, whereas the others depend quadratically on them. The models were optimized to maximize SB, BC, and SR and minimize FCR. The best results were obtained with a diet containing 80% silage and 20% corn bran, which produced larvae with 54.6% lipid and 34.9% crude protein. Conclusion: FS appears to be a promising substrate alternative for BSF rearing. CB, on the other hand, positively affects lipid production. In general, the diet optimized with FS and CB favors lipid production at the expense of crude protein in the larvae.