Total fishmeal replacement by defatted Hermetia illucens larvae meal in diets for gilthead seabream (Sparus aurata) juveniles

This work aimed to evaluate the digestibility of defatted Hermetia illucens larvae meal (HM), and its effects as fishmeal (FM) replacement on growth performance, feed and nutrient utilisation, and whole-body composition of gilthead seabream (Sparus aurata) juveniles. To assess apparent digestibility coefficients (ADC) of defatted HM, a reference-diet (43% crude protein (CP); 17% crude lipid (CL)) and a test-diet, in which 30% of the reference diet was replaced with defatted HM, were formulated. To assess the effect of dietary FM replacement, four isonitrogenous (43% CP) and isolipid (18% CL) diets were formulated to include defatted HM at 0 (HM0), 15 (HM15), 30 (HM30), and 45% (HM45), replacing FM at 0, 22, 60, and 100%, respectively. Triplicate groups of fish (initial body weight of 32 g) were randomly assigned to the experimental diets and the growth trial lasted for 67 days. The digestibility trials were conducted in a digestibility system, and each diet was tested in triplicate. Protein, lipid, and energy digestibility of defatted HM were high (>74%). Replacement of FM by defatted HM did not compromise the ADC of protein and lipid, while ADC of dry matter and energy increased. Complete dietary replacement of FM by defatted HM had no negative effects on growth performance, feed efficiency, whole-body composition, and protein utilisation of gilthead seabream juveniles, establishing the potential of defatted HM as an alternative ingredient for aquafeeds.