Effect of dietary Hermetia illucens larvae meal on triglyceride composition of sea bream fillets

Administering Hermetia illucens meal (HIM) to marine finfish can be considered a strategy to increase aquaculture sustainability. However, terrestrial insects contain little amounts of polyunsaturated fatty acids (PUFA) that could represent a limit in fish and human nutrition. Nevertheless, fatty acids distribution inside triglycerides (TGs) plays a pivotal role in fat digestion and absorption, due to the specificity of lipase activity on position sn-1 and sn-3. Since fatty acids in the sn-2 position are the first to be absorbed, our purpose was to analyze the FA profile of total lipids, triglycerides and their sn-2 position in fillets from gilthead sea bream (Sparus aurata L) fed HIM. Three-hundred and sixty gilthead sea bream were randomly divided into 12 tanks with four isoenergetic, isolipidic and isoproteic diets. Briefly, HI larvae meals were included at 9.2% (HI9), 18.4% (HI18), and 27.6% (HI27) in order to substitute graded levels of the FM contained in a control diet (HI0) which amount 30%. After 120 days of rearing, 10 fish for each diet were slaughtered and the fillet FA profile was deepened. The total lipid content was not affected by the diet. Considering the total lipid FA profile, in HI18 and HI27 fillets C12:0, C14:0, C16:1n-7, C18:1n-9 and the total saturated FA (SFA) content significantly increased while PUFAn-3 content lowered (p < .01). The triglyceride contents in the C, H25, HI18 and HI27 fillets were 2.65 ± 0.24, 3.07 ± 0.49, 3.28 ± 0.20, and 2.95 ± 0.21 g/100 g muscle, respectively. HI18 and HI27 fillets contained in their TGs higher level of C16:1n-9 and SFA (p < .05) than C and HI9 fillets. In the same groups, a slight but significant decrease in PUFAn-3 content was observed. Noticeably, the FA profile of the TG sn-2 position remained almost unaffected by the inclusion of HI in the diet. Indeed, only some SFAs, namely C12:0 and C14:0, significantly increased (p < .01) in the HI27 group whilst PUFAn-3 content did not vary. In conclusion, the effects observed on lipid FAs confirmed previous data on HI inclusion in aquafeeds for finfish. However, the changes appeared limited to the sn-1 and sn-3 position of TGs, thus highlighting the resilience of the sn-2 FA profile. Finally, this study evidenced that the inclusion of HI in the diet did not impair the presence of fatty acids important for human nutrition, as PUFAn-3 in the sn-2 position of triglycerides, increasing the chances of being better assimilated and absorbed.