Influence of Substrates on the Quality of Hermetia Meal for Fish Meal Substitution in Nile Tilapia Oreochromis niloticus

Commercially produced black soldier flies (Hermetia illucens) represent a promising fish meal substitute, particularly in the context of using agricultural by-products and waste. Here, the culture of Hermetia maggots on five selected substrates (potato protein (P) as a by-product of starch production, rapeseed oil cake (R) from rape oil production, maize silage (M), soybean (S) meal and, as a control, concentrated chicken feed (C)) were evaluated, assessing the growth performance of Hermetia maggots related to the overall production and the nutritional composition of the respective meal. Subsequently, their use as ingredients in aquafeed formulations was evaluated in a feeding trial with juvenile Nile tilapia Oreochromis niloticus, assessing the growth performance of the fish. Substrates used for Hermetia culture significantly affected the growth and development of the maggots, revealing substantial differences in the meal quality. Still, if incorporated in isonitrogenous and isocaloric diets (33% crude protein, 21-22 MJ/kg) replacing 75% of the fishmeal protein in the formulated diets, no significant differences in growth performance of the fish were observed compared to the fishmeal control. As a conclusion, substrates clearly affect the production yield and the composition of maggots. Nevertheless, this can be compensated by feed formulation as demonstrated by the feeding trial.