Genotype-by-Diet Interactions for Larval Performance and Body Composition Traits in the Black Soldier Fly, Hermetia illucens.

Further advancing black soldier fly (BSF) farming for waste valorisation and more sustainable global protein supplies critically depends on targeted exploitation of genotype-phenotype associations in this insect, comparable to conventional livestock. This study used a fully crossed factorial design of rearing larvae of four genetically distinct BSF strains (FST: 0.11-0.35) on three nutritionally different diets (poultry feed, food waste, poultry manure) to investigate genotype-by-environment interactions. Phenotypic responses included larval growth dynamics over time, weight at harvest, mortality, biomass production with respective contents of ash, fat, and protein, including amino acid profiles, as well as bioconversion and nitrogen efficiency, reduction of dry matter and relevant fibre fractions, and dry matter loss (emissions). Virtually all larval performance and body composition traits were substantially influenced by diet but also characterised by ample BSF genetic variation and, most importantly, by pronounced interaction effects between the two. Across evaluated phenotypes, variable diet-dependent rankings and the lack of generally superior BSF strains indicate the involvement of trade-offs between traits, as their relationships may even change signs. Conflicting resource allocation in light of overall BSF fitness suggests anticipated breeding programs will require complex and differential selection strategies to account for pinpointed trait maximisation versus multi-purpose resilience.

Transfer of Lauric and Myristic Acid from Black Soldier Fly Larval Lipids to Egg Yolk Lipids of Hens Is Low.

Implementing insects, such as the black soldier fly larvae (BSFL), as animal feed commonly includes the previous removal of substantial amounts of fat. This fat may represent an as yet underutilized energy source for livestock. However, transfer of lauric and myristic acid, prevalent in BSFL fat and undesired in human nutrition, into animal-source foods like eggs may limit its implementation. To quantify this, a laying hen experiment was performed comprising five different diets (10 hens/diet). These were a control diet with soybean oil and meal and a second diet with soybean oil but with partially defatted BSFL meal as protein source. The other three diets were based on different combinations of partially defatted BSFL meal and fat obtained by two different production methods. Lauric acid made up half of the BSFL fat from both origins. Both BSFL fats also contained substantial amounts of myristic and palmitic acid. However, in the insect-based diets, the net transfer from diet to egg yolk was less than 1% for lauric acid, whereas the net transfer for myristic and palmitic acid was about 30% and 100%, respectively. The net transfer did not vary between BSFL originating from production on different larval feeding substrates. The results illustrate that hens are able to metabolize or elongate very large proportions of ingested lauric acid and myristic acid, which are predominant in the BSFL lipids (together accounting for as much as 37 mol%), such that they collectively account for less than 3.5 mol% of egg yolk fatty acids.