48 JUNE 2025 • WORLD AQUACULTURE • WWW.WAS.ORG supplemented groups, especially with whole BSFL inclusion at 5%. Mineral analysis further indicated that BSFL supplementation helped restore essential minerals, such as sulfur and zinc, which were adversely affected by high SBM inclusion. Enhanced gut health: Histopathological examinations indicated substantial improvements in intestinal health among fish fed BSFL-supplemented diets. Specifically, diets with 5% whole BSFL significantly reduced intestinal inflammation and improved gut epithelial structure compared to the SBM-only diet (Figure 4). Defense against bacterial challenge: 5% inclusion of whole-BSFL helped maintain gut health, immune response, and higher survival rates in fish challenged with Flavobacterium psychrophilum, comparable to fishmeal-based diets. BSFL supplementation effectively maintained intestinal morphology, elevated dietary and whole-body lauric acid levels, and supported immune-related gene expression (IL-8, TNF-α, and C5). Economic and Practical Considerations for Future Research Directions While BSFL presents substantial promise as a sustainable ingredient in aquafeed, its practical application at a large scale remains limited by biological and economic constraints. Rather than aiming to replace fishmeal entirely, our research insights advocate for the strategic use of BSFL at moderate inclusion levels (~5%) as a functional feed ingredient. This approach balances metabolic and immunological benefits with economic viability and aligns with the realistic feed industry world. FIGURE 4. Distal intestinal histology of rainbow trout fed control, fishmealbased diet (a), soybean meal (SBM)-based diet (b), and 5% whole BSFL supplemented SBM-based diet (c) for 10 weeks. The SBM-based diet, without supplementation, showed more inflammatory cells (ic) and mucous cells (mc). H&E staining at X 200 magnification (By Nicholas Romano, USDA-ARS, Fort Pierce, FL, USA). FIGURE 5. Estimated cost of production among the four largest BSFL producers (by funds raised) (Source: Shah and Jules (2024), Rethink Priorities). FIGURE 6. Beneficial role of BSFL as a functional feed ingredient in trout diet [Based on the research study by Singha et al. (2025)].
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