Insect larvae meal as a complementary functional ingredient in high soybean meal-based diets improve the health of rainbow trout (Oncorhynchus mykiss)

Authors: Ma, Jie; SINGHA, KRISHNA - University Of Idaho; ABANIKANNDA, MOSOPE - University Of Idaho; MYRSELL, VERONICA - University Of Idaho; Romano, Nicholas; KOUTSOS, ELIZABETH - Enviroflight Llc; ADAMS, DANIEL - Enviroflight Llc; KUMAR, VIKAS - University Of Idaho

Submitted to: Journal of Fish Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/2025
Publication Date: 7/7/2025
Citation: Ma, J., Singha, K.P., Abanikannda, M.F., Myrsell, V., Romano, N.P., Koutsos, E., Adams, D., Kumar, V. 2025. Insect larvae meal as a complementary functional ingredient in high soybean meal-based diets improve the health of rainbow trout (Oncorhynchus mykiss). Journal of Fish Diseases. 2025(48):e14153. https://doi.org/10.1111/jfd.14153.
DOI: https://doi.org/10.1111/jfd.14153

Interpretive Summary: This study delves into the use of black soldier fly larvae (BSFL) to enhance the inclusion of soybean meal (SBM) in rainbow trout diets. Six different diets were tested, including a fishmeal-based control, an SBM-based diet, and variations with 2.5% and 5% whole-body (WB) or defatted (DB) BSFL supplementation. The results showed that adding BSFL improved gut health, immune response, and survival rates when fish were challenged with a pathogen. Higher levels of dietary lauric acid from BSFL led to increased whole-body lauric acid. Fish on BSFL diets had better survival rates against infections, especially those on the WB5 diet. Improved intestinal health was noted in BSFL-fed fish, with no signs of pathogenic enteritis. Gene expression indicated a stronger immune response in these fish. The study concludes that BSFL can effectively complement SBM, boosting health and performance in rainbow trout, and provides an economically viable alternative to traditional protein sources.

Technical Abstract: This study explores the integration of black soldier fly larvae (BSFL) as a complementary functional ingredient to increase the soybean meal (SBM) inclusion in rainbow trout (Oncorhynchus mykiss) diets. Six experimental diets were formulated, including a control diet as fishmeal (FM), an SBM-based diet, and 2.5 and 5% whole-body (WB) or defatted (DB) BSFL-supplemented SBM-based diets. Results revealed that BSFL inclusion positively influences gut health, immune response, and survival rates following challenge with Flavobacterium psychrophilum. Dietary lauric acid content significantly impacted whole-body lauric acid levels in a dose-dependent manner, with BSFL diets showing higher levels than FM and SBM diets. Fish fed diets with BSFL exhibited enhanced survivability against F. psychrophilum infection compared to SBM-fed fish, with the highest survival rates observed in the WB5 (5% whole-body BSFL) group. Histological analysis demonstrated improved intestinal morphology in BSFL-fed fish, particularly evident in the absence of pathogenic enteritis. Gene expression analysis revealed upregulated proinflammatory markers (IL-8, TNF-'', C5) in BSFL-fed fish post-challenge, indicating an enhanced immune response. These findings indicate the potential of BSFL as a functional feed component to enhance the SBM inclusion in rainbow trout with improved health and performance. By strategically reducing inclusion levels and positioning BSFL as a complement to traditional protein sources, aquafeed formulations can mitigate economic concerns while maximizing the benefits of this sustainable alternative.