Comparison of black soldier fly, cricket, and superworm on growth performance, nutrient utilization and fatty acid profiles of rainbow trout

Inclusion of fishmeal and fish oil in feeds for farmed fish is not sustainable and alternatives need to be evaluated. The aim of this study was to determine the effect of diets including defatted black soldier fly larvae ( Hermetia illucens ), adult cricket ( Gryllodes sigillatus ) and superworm ( Zophobas morio ) on the growth performance, apparent nutrient digestibility, nutrient retention, and fatty acid profiles of juvenile rainbow trout ( Oncorhynchus mykiss ). Triplicate tanks of fish (100.5 ± 0.6 g; mean ± SD) were fed one of four diets, a control diet with 20% fishmeal, and three experimental diets containing either 15% defatted black soldier fly meal, 15% full-fat adult cricket meal or 15% full-fat superworm meal, where each insect meal partially replaced fishmeal and fish oil. After 84 days of feeding, no significant differences were observed between diets for growth performance indicators or body indices. Fish fed the control and superworm diets had a higher protein content and retention in whole-body carcass compared to the cricket and black soldier fly diet groups. No significant effects between diets were found on whole-body carcass regarding fatty acid classes SFA, MUFA, PUFA n-3 and PUFA n-6, although lauric acid and myristic acid were significantly higher in fish fed black soldier fly diet and linoleic acid was higher in fish fed superworm and cricket diets. Retention of fatty acids was higher for most classes in fish fed the black soldier fly diet, yet whole carcass lipid content did not differ significantly between diets. Additionally, apparent digestibility of phosphorous was significantly improved for all insect diets compared to the control. These results indicate that insect meals can partially replace fishmeal and fish oil in diets for rainbow trout without compromising growth performance and fatty acid composition, while improving phosphorous utilization.