Abstract
Black soldier fly larvae (BSFL) meal is a promising sustainable protein source for aquafeeds. Processing BSFL into meal and oil can be based on wet rendering technology where the raw material is heat treated and mechanically separated into press cake, stickwater (SW), and oil. In this study, to verify the effect of SW reincorporation into the press cake, dried BSFL cake and SW meal were included in feed mixes before extrusion. Four experimental feeds were prepared, containing 100 g kg(-1) BSFL meal with a cake/SW ratio of 100/0, 90/10, 80/20 and 60/40 g kg(-1), respectively and compared to a control feed in a trial with Atlantic salmon parr reared in freshwater. The feeds had similar nutritional value and all feeds were highly digestible. The highest content of manganese (Mn) was found in the BSFL cake feed (120 mgkg(-1)), was reduced with increased SW inclusion and lowest in the control feed. There were no dietary differences in growth or welfare with increased SW inclusion, and no negative impact of high dietary Mn levels. The high Mn content was not accumulated in the fish, and only resulted in an increased excretion of Mn. Further studies are needed to verify these results in Atlantic salmon postsmolt.