Insect (black soldier fly, Hermetia illucens) meal supplementation prevents the soybean meal-induced intestinal enteritis in rainbow trout and health benefits of using insect oil

• Published in: Fish & shellfish immunology 2021-02, Vol.109, p.116-124
• Main Authors: Kumar, Vikas, Fawole, Femi J., Romano, Nicholas, Hossain, Md Sakhawat, Labh, Shyam N., Overturf, Ken, Small, Brian C.
• Format: Article
• Language: English
• Subjects: Animal Feed - analysis; Animals; Bile acid; Black soldier fly larvae meal and oil; Diet - veterinary; Dietary Supplements - analysis; Diptera - chemistry; Diptera - growth & development; Dose-Response Relationship, Drug; Enteritis - chemically induced; Enteritis - prevention & control; Enteritis - veterinary; Fish Diseases - chemically induced; Fish Diseases - prevention & control; Glycine max - adverse effects; Immune genes; Inflammation; Intestinal enteritis; Intestines - physiopathology; Larva - chemistry; Larva - growth & development; Oncorhynchus mykiss - immunology; Rainbow trout; Soybean meal
• ISSN: 1050-4648; 1095-9947
• DOI: 10.1016/j.fsi.2020.12.008

Black solider fly larvae (BSFL) and their oils (BSFLO) are receiving increasing attention as sustainable ingredients in fish feeds, but mostly as replacements to marine sources. There were two aims to this study; in exp. 1, soybean meal (SBM)-based diets were formulated to contain BSFL as supplements at 0 (SBM), 8 (SBM + BSFLlow) or 16% (SBM + BSFLhigh) with a control diet being fishmeal-based (FM). In exp. 2, diets included only fish oil (FO), soybean oil (SBO), BSFLO or BSFLO + bile acid (BA), and all lipid sources were added at 16%. Both experiments were run at the same time and fed to rainbow trout (32 g) with each treatment being triplicated. After 10 weeks the fish were sampled for liver and distal intestine histology, expression of genes responsible for inflammation in the intestine and kidneys, and serum peroxidase and lysozyme activities. In exp. 1, supplementations of BSFL effectively prevented SBM-induced intestinal enteritis, down-regulated intestinal prostaglandin and interferon regulatory factor 1 (IRF-1), while the SBM + BSFLhigh diet significantly increased serum lysozyme activity. In exp. 2, BSFLO caused no histomorphological change to the liver or intestine, but kidney interluekin-8, tumor necrosis factor and IRF-1 were significantly upregulated along with significantly higher serum peroxidase activity. The inclusion of BA in the BSFLO diets significantly upregulated intestinal prostaglandin gene expression. Overall, BSFL supplementations of 8 or 16% prevented SBM-induced intestinal enteritis based on histological observations, which was supported by a down-regulation in pro-inflammatory genes and enhanced innate immunity. Meanwhile, the use of BSFLO showed some immunological benefits. Therefore, these sustainable resources are recommended in the diets of rainbow trout, especially when using elevated levels of plant-based proteins. •This study identified black solider fly larvae (BSFL) and their oils (BSFLO) as novel feed ingredients for rainbow trout.•Supplementation of BSFL meal mitigated the soybean meal-induced intestinal enteritis based on histological observations.•Inclusion of BSFL in SBM based diets down-regulated the pro-inflammatory genes and enhanced innate immunity.•Fish oil or soybean oil can be replaced with BSFLO with no histopathological changes in the liver or intestine.•Addition of dietary BSFLO decreased inflammation and improved immunity and innate immunity parameters.