Assessment of Hermetia illucens larvae performance reared on raw or contaminated peanut by-products with Aspergillus flavus and Fusarium graminearum

The peanut supply chain is characterised by a high production of by-products, mainly shells and small pods, often discarded by processing companies. However, the richness of nutritive substances makes these products valuable as feed substrates for Hermetia illucens larvae rearing. Therefore, the aims of this work were to (1) evaluate the performance of H. illucens larvae reared on peanut by-products and (2) study the effect of various levels of fungal contamination in by-products on H. illucens larvae performance, focusing on growth and mortality. Two agro-industrial peanut by-products (rich by-product, R; poor by-product, P) were ground and mixed in different percentages (0-100%, step 10%) to obtain 11 different feeding substrates, then rehydrated to 70% moisture. Three different trials were conducted using these substrates, with three-day-old H. illucens larvae reared for 10 days. Whereas, the effect of fungal contamination was investigated by inoculating chicken feed (standard, S) and substrate P5R5 (50% P and 50% R) with two spore suspensions (Aspergillus flavus and Fusarium graminearum, 105 spore/mL), at three different inoculation times (5, 3 and 0 days before the addition of larvae). The substrate composition considerably impacted larval growth, with the highest larval weight increase obtained when R reached 50% in the substrate. Fungal contamination in by-products significantly reduced larvae performance, with a stronger negative effect from A. flavus. These findings suggest the potential for enhancing peanut by-products as a rearing substrate for H. illucens larvae, although the composition and the possible fungal contamination may reduce the effectiveness of the process.