Meat-based substrates in black soldier fly larvae rearing: impacts on growth performance and nutritional value

The main interest of insect farming lies in their potential to be reared on unexploited substrates. The black soldier fly (BSF, Hermetia illucens) can be reared on a wide variety of substrates and in a short time. In Europe, farmed insects cannot be fed on substrates that contain meat or fish, which would increase the impact of the sector in reducing food losses. This study aimed to investigate the effects of meat-based diets on growth performance and chemical composition of BSF larvae. A Gainesville diet (plant based) was used as a control substrate (C), and two further substrates were formulated by mixing 75% Gainesville + 25% raw (R) or processed (P) meat. Larvae reared on meat-based substrates had significantly higher growth rates and efficiency of conversion index (ECI), along with a lower feed conversion ratio (FCR). Despite the differences in crude protein content of the substrates, the larvae did not exhibit significant variations in protein levels according to the diets, while the fat contents of substrates were reflected, with R larvae having the highest content. The R larvae also presented the lowest rate of SFA and the highest content of MUFA. Differences in the amino acid profile of BSF larvae were scarce, while the mineral content was strictly related to the composition of the substrates. Meat-based substrates promote a good nutritional quality of larvae and faster growth than plant-based substrates. These findings highlight the potential of BSF to contribute significantly to a circular economy system and in reducing food losses.HIGHLIGHTS Meat-based substrates enhanced the growth performance of larvae. The protein content of larvae was not affected by the substrates. The substrates influenced the fat quality of larvae. Meat had a minimal impact on the amino acid contents of larvae.