BEYOND PROTEIN: Hermetia Illucens-BASED INGREDIENTS AS FUNCTIONAL PERFORMANCE AND GUT HEALTH DRIVERS FOR FISH
Introduction
Beyond their value as a source of protein, Hermetia illucens-derived ingredients exhibit underexploited functional potential in salmonid nutrition. Their water-soluble fraction, rich in bioactive compounds, such as nucleotides, free amino acids or short-chain peptides are posited to stimulate feed intake and enhance zootechnical performance, while antimicrobial peptides, lauric acid, and chitin could support immunity and gut robustness. Recent industrial advances in black soldier fly larvae (BSFL) production now ensure consistent product quality, enabling reliable expression of these functional effects. This study therefore evaluates BSFL meal as a booster of feed intake, efficiency, and gut health in grower Atlantic salmon (Salmo salar).
Materials and Methods
In this saltwater trial, adult salmon (~300 g) were fed to apparent satiation three times daily for twelve weeks in randomized quadruplicates. Four diets were tested: a reference diet (CTL) based on fishmeal (18%) and soy protein concentrate (SPC, 25%), and three experimental diets including BSFL meal at respectively 2.5% (BSFL2.5), 5% (BSFL5), and 10% (BSFL10) inclusion rates as an SPC replacement. Daily feed intake as well as initial and final body weights were recorded to calculate standard zootechnical performance indicators (weight gain, WG; specific growth rate, SGR; feed conversion ratio, FCR). Gut samples were also taken for histology analysis: ranking of the gut inflammatory status, villi length, and submucosal thickness.
Results
During this trial, feed intake was found to be increased linearly with dietary BSFL inclusion (423 g/fish for CTL diet to 457 g/fish for BSFL10 diet). Beyond the increased intake, insect meal inclusion also improved feed efficiency, as demonstrated by a significantly higher WG in the 10% BSFL group (+11%, P = 0.02) and a reduced FCR in this same group compared to the CTL group (0.90 vs. 0.93; P = 0.004). Salmon fed the BSFL2.5 diet demonstrated a significantly improved protein retention efficiency (44.2% for BSFL2.5 vs. 40.3% for CTL diet, P = 0.001). Compared to the control, the BSFL-fed groups showed a lower proportion of fish with elevated gut inflammation (Figure 1). Although villus length was not significantly affected by treatment, fish receiving the BSFL meal showed a numerical increase in villus length, which might indicate enhanced nutrient absorption. Concurrently, submucosal thickness was numerically reduced in the BSFL-fed groups compared to the control (P = 0.099), providing further evidence of reduced inflammatory effects.
Figure 1: Effects of Dietary Black Soldier Fly Larvae (BSFL) Inclusion on Growth Performance, Feed Efficiency, and Gut Health of adult Atlantic salmon.
Discussion
The results of this study confirm that Hermetia illucens meal is a highly functional alternative to traditional protein sources, capable of enhancing both zootechnical performance and intestinal integrity of Atlantic salmon. The physiological basis for these improvements likely stems from the unique bioactive profile of BSFL protein and its positive influence on gut health. The compounds stated previously are recognized for their benefits on intestinal microbiota, natural immunity and stress resilience, and attractivity/palatability. The observed linear increase in feed intake and significant improvements in weight gain and FCR align with previous findings that BSFL meal inclusion can improve growth rates and feed efficiency in juvenile salmon1, and more broadly fish aquatic species2,3. Our histological observations also support existing research indicating that BSFL meal does not compromise gut health4 and positively modulates gut microbiota5 of fish.
In conclusion, by demonstrating their functional value in adult Atlantic salmon, these findings confirm that BSFL-derived ingredients can serve as performance drivers beyond their sole nutritional and environmental value.
References
1. Deguara, S. et al. Enhanced Growth and Feed Efficiency in Freshwater Atlantic Salmon through Partial Fishmeal Replacement with Insect Meal. Innovafeed Whitepaper (2025).
2. Cho, J.-H. et al. Effects of black soldier fly (Hermetia illucens) pre-pupae meal on the growth, stress, and immune responses of juvenile rainbow trout (Oncorhynchus mykiss) reared at different stocking densities. Aquaculture Reports 25, 101202 (2022).
3. Liu, Y. et al. A preliminary study on the effects of substituting fishmeal with defatted black soldier fly (Hermetia illucens) larval meal on Asian seabass (Lates calcarifer) juveniles: Growth performance, feed efficiency, nutrient composition, disease resistance, and economic returns. Journal of Fish Biology 105, 1681–1693 (2024).
4. Li, Y. et al. Gut health and vaccination response in pre-smolt Atlantic salmon (Salmo salar) fed black soldier fly (Hermetia illucens) larvae meal. Fish & Shellfish Immunology 86, 1106–1113 (2019).
5. Moutinho, S. et al. Use of black soldier fly (Hermetia illucens) larvae meal in diets for gilthead seabream juveniles: Effects on growth-related gene expression, intermediary metabolism, digestive enzymes, and gut microbiota modulation. Aquaculture 580, 740357 (2024).