Dietary inclusion of black soldier fly, cricket and superworm in rainbow trout aquaculture: impacts on growth and nutrient profiles

Inclusion of fishmeal and fish oil in aquafeeds is unsustainable, prompting the need for alternative protein and lipid sources. This study evaluates the impact of diets incorporating defatted black soldier fly larvae (Hermetia illucens), adult cricket (Gryllodes sigillatus) and superworm (Zophobas morio) on the growth performance, nutrient digestibility, nutrient retention efficiency, fatty acid and amino acid profiles of juvenile rainbow trout (Oncorhynchus mykiss). Juvenile trout (100.5 ± 0.6 g; mean ± SD) were fed one of four diets: a control diet with 20% fishmeal, and three experimental diets containing a total of 15% defatted black soldier fly meal, full-fat adult cricket meal, or full-fat superworm meal, with partial replacement of fishmeal and fish oil. Growth performance and body indices were unaffected by dietary treatments. Whole carcass content and retention efficiency of protein were higher in fish fed the control and superworm diets compared to those on cricket and black soldier fly diets. Despite reduced retention efficiency of leucine, phenylalanine, glutamic acid, and serine, carcass amino acid contents were not affected by dietary treatment. Fatty acid retention efficiency was greater in fish on the black soldier fly diet, though overall lipid content was consistent across diets. Notably, lauric acid and myristic acid levels were elevated in the black soldier fly group, while linoleic acid was higher in fish fed the superworm and cricket diets. Phosphorus retention improved significantly with the black soldier fly treatment, yet nitrogen retention was reduced. These findings suggest that insect meals can partially replace fishmeal and fish oil in trout diets without compromising growth or fatty acid composition.