ω3-enrichment of Hermetia illucens (L. 1758) prepupae from oilseed byproducts

Abstract

To meet the growing demand for fish in human nutrition, aquaculture is developing increasingly from marine fishery products ( i.e. fish meal and fish oil). New environmentally sustainable protein and lipid resources are recommended for this sector and insects, particularly black soldier fly (BSF), Hermetia illucens (L. 1758), are considered as promising candidates for fish feed production. BSF larvae convert organic materials into high-valued protein and lipid, their nutritional composition is related to their diet and could therefore be manipulated. The key issue in fish nutrition will be the fatty acid composition of BSF larvae that are characterized by high saturated fatty acids (SFAs) level (>60%) with lack of essential polyunsaturated fatty acids. This study aimed to adjust the fatty acid profile of BSF larvae by manipulating their food on focusing on diet formulation with local oilseed cakes for essential ω3 fatty acid (ALA: α-linolenic acid, C18:3n3) enrichment. Selected populations (100 individuals/population) of 7 days old BSF larvae were reared on Chicken feed (CF) diets enriched with flax and rape cakes at six incorporation rates (10–20 − 40–60 − 80–100%), the CF was used as the control diet and all diets were tested in triplicate (n = 3). The first prepupae appeared from 15 rearing days on all diets with an average weight of 195 mg excepted for full oil cake diets showing longer prepupal collection time (7 days) and lower average weight (116 mg). Oil cakes incorporation shows an impact on the prepupae fatty acid profiles. The results show that progressive oil cakes diets incorporation decreased saturated fatty acids from 75.86 ± 0.34% to 56.10 ± 0.74%. Simultaneously, rape cake incorporation leads mainly to oleic acid (C18:1n-9) enrichment which not sought in fish nutrition and low ALA rate from 1.16 ± 0.25% to 2.42 ± 0.12% but Flax cake incorporation increase ALA enrichment up till 15.27 ± 0.02% favorable to fish needs allowing a potential increase BSF meal incorporation in fish feed. This research therefore presents a model of progressive prepupae oil enrichment from oilseed coproducts for application in fish feed.