Insect substrates: evaluation of efficiency indices

Larvae of the black soldier fly (BSF), Hermetia illucens L. (Diptera: Stratiomydae), are able to convert organicmaterial (i.e. waste and by products) into high-quality biomass, which can be processed into animal feed.Although, several studies have been conducted on evaluation of influence of growing substrate on thenutritional value of BSF larvae and prepupae, this field need more accurate investigation. The intent of thiswork was to collect, synthesize, discuss and review the available information on the substrates used for rearingBSF larvae in literature. Data collected were furtherly elaborated to estimate of the food conversion rate (FCR)and efficiency of conversion of ingested food (ECI)for BSF larvae. In light of this, a systematic review based on16 publications published from 2008 to 2021 was carried out in order to evaluate the effects rearing substrateon deriving insect’s biomass. Based on selected studies it can be suggested that BSF is able to convert organicmaterial (i.e. waste and by products) into high-quality biomass. The role and effects of selected nutrients, suchas ether extract/fats, carbohydrates and fibre in the substrate, seem to be key factors in defining the featuresof the biomass as well as the time needed to reach the harvesting state. With regard to FCR, a wide variabilitywas observed ranging from 2 up to 20, while in the case of ECI value ranged between 3.4% and 54%. In the frameof the present study it has been observed that very low FCR or high ECI seems to be related to longer larvaedeveloping time. The BSF larvae can be considered efficient “farmed animal” when nutritionally appropriatesubstrates are used. Furtherly the high levels of protein produced by the BSF larvae make these insects a veryimportant resource for the animal feed formulation.