BACKGROUND: Black soldier fly larvae are converters of organic waste into edible biomass, of which the composition may depend on the substrate. In this study, larvae were grown on four substrates: chicken feed, vegetable waste, biogas digestate, and restaurant waste. Samples of prepupae and substrates were freeze‐dried and proximate, amino acid, fatty acid and mineral analyses were performed.RESULTS: Protein content of prepupae varied between 399 and 431 g kg⁻¹ dry matter (DM) among treatments. Differences in amino acid profile of prepupae were small. On the other hand, the ether extract (EE) and ash contents differed substantially. Prepupae reared on digestate were low in EE and high in ash (218 and 197 g kg⁻¹ DM, respectively) compared to those reared on vegetable waste (371 and 96 g kg⁻¹ DM, respectively), chicken feed (336 and 100 g kg⁻¹ DM, respectively) and restaurant waste (386 and 27 g kg⁻¹ DM, respectively). Prepupal fatty acid profiles were characterised by high levels of C12:0 in all treatments.CONCLUSION: Since protein content and quality were high and comparable for prepupae reared on different substrates, black soldier fly could be an interesting protein source for animal feeds. However, differences in EE and ash content as a function of substrate should be considered. © 2016 Society of Chemical Industry

Feed security, feed quality and issues surrounding the safety of raw materials are always of interest to all livestock farmers, feed manufacturers and competent authorities. These concerns are even more important when alternative feed ingredients, new product developments and innovative feeding trends, like insect-meals, are considered. The black soldier fly (Hermetia illucens) is considered a good candidate to be used as feed ingredient for aquaculture and other farm animals, mainly as an alternative protein source. Data on transfer of contaminants from different substrates to the insects, as well as the possible occurrence of toxin-producing fungi in the gut of non-processed insects are very limited. Accordingly, we investigated the impact of the substrate/diet on the intestinal mycobiota of H. illucens larvae using culture-dependent approaches (microbiological analyses, molecular identification through the typing of isolates and the sequencing of the 26S rRNA D1/D2 domain) and amplicon-based next-generation sequencing (454 pyrosequencing). We fed five groups of H. illucens larvae at the third growing stage on two substrates: chicken feed and/or vegetable waste, provided at different timings. The obtained results indicated that Pichia was the most abundant genus associated with the larvae fed on vegetable waste, whereas Trichosporon, Rhodotorula and Geotrichum were the most abundant genera in the larvae fed on chicken feed only. Differences in the fungal communities were highlighted, suggesting that the type of substrate selects diverse yeast and mold genera, in particular vegetable waste is associated with a greater diversity of fungal species compared to chicken feed only. A further confirmation of the significant influence of diet on the mycobiota is the fact that no operational taxonomic unit common to all groups of larvae was detected. Finally, the killer phenotype of isolated yeasts was tested, showing the inhibitory activity of just one species against sensitive strains, out of the 11 tested species.

The black soldier fly, Hermetia illucens (L.), shows potential as a resource for animal feed. However, industrial production in regions where the insect is not native, like northwestern Europe, could lead to permanent establishment, which might entail environmental risks. In temperate climates, establishment depends on the insect’s ability to overwinter. This study assessed the insect’s cold hardiness by determining the supercooling point (SCP) and lower lethal time at 5 °C (LTime_10,50,90) for different life stages. As diet or acclimation can influence cold hardiness, prepupae reared on different substrates and acclimated prepupae were tested in separate experiments. The SCP ranged from −7.3 °C for late-instar larvae to −13.7 °C for pupae. Prepupae reared on a highly nutritional substrate had a lower SCP compared with a control diet composed of chicken feed (−14.1 °C vs. −12.4 °C, respectively), whereas the SCP was unaffected by acclimation. Based on the LTime, prepupae and pupae were the most cold hardy life stages. Acclimated prepupae were most cold tolerant, with a LTime₅₀ of 23 d. Based on an empirical relationship between LTime₅₀ and field survival of various arthropods, it was predicted that H. illucens would survive about 47 d in the field during northwestern European winters. The results from this laboratory study suggest that H. illucens is rather unlikely to overwinter in northwestern Europe. However, caution is warranted given that diet and acclimation can influence the insect’s cold hardiness and in the field the insect may survive in a diapausing state or in protected hibernacula.