The bioconversion of hatchery residues (HR; unmarketable chicks, eggs and eggshells) by black soldier fly larvae (BSFL) offers an alternative to conventional rendering. Fermentation of HR improves microbiological quality and odours but results in carbohydrate-deficient diets. This study assessed the potential of BSFL to bioconvert fermented and unfermented HR diets and evaluated the impact on resulting larvae and frass. Diets included a control (Gainesville), unfermented HR, and fermented HR (14 days, 0.3% ferment, 25% lactose, dry basis), with or without 13% potato residues (dry basis) as a carbohydrate source. The BSFL (n = 800 5-day post-eclosion neonates) were reared in triplicate per treatment (0.6 g dry diet/larva). Microbiological analyses were performed on diets, larvae, and frass. Yield and bioconversion rate were significantly lower for unfermented (60 ± 7 g; 5%) and fermented HR (19 ± 4 g; 2%) than for the control (209 ± 18 g; 14%). Fermentation effectively reduced initial coliform loads to values (< 2 log cfu/g) below those of the control (4 log cfu/g) and unfermented HR (5 log cfu/g) but failed to control spore-forming Clostridium spp. (8 log cfu/g in diets; 9 log cfu/g in larvae). Larvae and frass from the control exhibited higher contamination with Salmonella spp. and Listeria monocytogenes (4–5 log cfu/g) than those from unfermented HR (3 log cfu/g). These findings indicate that HR can support BSFL rearing, though further composition and texture optimisation is required. While fermentation enhances initial substrate quality, post-harvest treatments of larvae remain essential to ensure microbial safety. • HR can be used as BSF diet but require macronutrient and texture optimisation • Fermentation impairs texture, causing liquefaction and higher larval mortality • Fermentation improves initial microbiological quality, but recontamination occurs • Adding potato residues as a carbohydrate source does not improve bioconversion • Plant-based diets may carry more Salmonella spp . and L. monocytogenes than HR diets
Dallaire-Lamontagne et al. (Tue,) studied this question.