The fatty acid composition of black soldier fly larvae: the influence of feed substrate and applications in the feed industry

The need to reduce, reuse and recycle materials by applying new strategies of circular economy instead of linear systems of disposal is becoming increasingly urgent. The black soldier fly (BSF), Hermetia illucens (L) (Diptera: Stratiomyidae), is being studied for its outstanding capacity to convert organic waste into high-value biomass and as a valuable nutrient source for animal feed. A systematic literature review identified 35 articles on BSF rearing and use in animal feed. This review summarizes our current knowledge about the lipid composition of BSF larvae, in particular their fatty acid (FA) profile and the mechanisms through which the feeding substrate influences the FA profile. BSF larvae are shown to synthesize certain FAs, such as lauric and myristic acid, even when these components are absent from their diet. Furthermore, enriching the rearing substrate with eicosapentaenoic and docosahexaenoic acid is reported to increase the accumulation of these FAs. The saturated FA content increases when BSF larvae are reared on a vegetable-based diet. Moreover, enriching the rearing media with materials high in omega-3 and omega-6 FAs increases their concentration in the larvae and enhances their value as a feed substrate for other animals. Indeed, the supplementation of animal feeds with BSF larvae products is being studied for application in the aquaculture, poultry, and pig farming sectors. BSF larval fats are shown to have a positive effect on animal growth performances, body composition, and gut histology, establishing BSF larvae as an environmentallysustainable feed ingredient. This review highlights the importance of deepening our knowledge on the various aspects of BSF larvae rearing and treatments which enhance the accumulation of specific lipids and minimize lipid quality deterioration and loss. By summarizing the existing literature on BSF larvae, this article contributes to the advancement of circular economies and the development of sustainable feed practices.