Partial dietary fishmeal replacement with full-fat or defatted superworm (Zophobas morio) larvae meals modulates the innate immune system of gilthead seabream, Sparus aurata

Full-fat and defatted superworm Zophobas morio larvae meals were used in a feeding trial of 540 gilthead seabream, Sparus aurata, juveniles (3.4 g initial weight) in order to assess their immunomodulatory effects. Six isonitrogenous (52 %) and isoenergetic (21 MJ/Kg) diets were formulated where the fishmeal of the control diet was replaced by full-fat Z. morio meal at 5 % and 10 % (FF5 and FF10) or defatted Z. morio meal at 10, 20 or 30 % (LF10, LF20 and LF30). Fish were kept in 18 glass tanks (125 L) within a closed recirculation seawater system and fed to satiation twice a day, 6 days per week for 100 days. LF20 significantly increased the percentage of neutrophils compared to a control fish-fed fishmeal (FM)-based diet. The dietary Z. morio meal immunomodulated the fish as expressed through an increased complement-associated bacterial killing (FF5 and FF10), nitric oxide production (LF30), and a tendency for an increased activity of lysozyme (FF5, LF20 and LF30) and of myeloperoxidase (FF5 and LF20), while trypsin inhibition was significantly suppressed by dietary FF5 and all 3 LF-containing diets compared to control FM-fed fish. These findings suggest that dietary Z. morio can immunomodulate gilthead seabream but further infectious challenge studies will have to be performed to determine if these effects are translated into an increased resistance to diseases. © 2022 The Authors