Effects of black soldier fly (Hermetia illucens) enriched with Schizochytrium sp. on zebrafish (Danio rerio) reproductive performances

Nutrient quality, with emphasis on lipid and fatty acid composition of broodstock diet, is one of the major dietary factors influencing fish oocytes maturation, reproductive success and offspring quality/survival. The Black Soldier Fly (BFS) (Hermetia illucens) is a valuable insect species characterized by a balanced essential amino acid profile comparable to fishmeal and has been demonstrated to be an eco-friendly and low-cost protein source in fish diets. However, as regards lipids, BFS is usually characterized by a poor content in polyunsaturated fatty acids which are essential for fish during critical life-cycle stages including oocyte maturation and reproduction. In the present study, full-fat enriched BSF prepupae meal was obtained from BSF larvae reared on coffee by-product (coffee silverskin) enriched with 10% of Schizochytrium sp. Successively, five experimental diets containing different full-fat enriched BSF prepupae meal inclusion levels (corresponding to the 0, 25, 50, 75 and 100% fish meal replacement) were tested during a six-month feeding trial performed on zebrafish (Danio rerio) to investigate, for the first time, the physiological effects on female fish growth, stress response, lipid metabolism and reproductive performances. A multidisciplinary approach including biometric, gas-chromatographic, histological and molecular analyses was used during the present study to have a comprehensive overview of fish responses to the test diets. Results highlighted that up to 50% of fish meal replacement with enriched BSF meal did not impair zebrafish physiological responses while higher replacement levels (75 and 100%) negatively affected fish stress response, oocytes maturation stages, spawning and hatching success.