Lipid and fatty acid digestibility in Calanus copepod and krill oil by Atlantic halibut (Hippoglossus hippoglossus L.)

Abstract

Marine zooplankton represent a significant biomass of marine lipid that could supply lipid in diets for farmed marine fish. Digestibility of lipid and fatty acids of the copepod, Calanus finmarchicus and Antarctic krill, Euphausia superba by farmed juvenile Atlantic halibut (Hippoglossus hippoglossus) was investigated. Halibut were fed diets containing one of the following test oils at 15% inclusion level: fish oil (FO), Calanus copepod oil (CO) and Euphausia krill oil (KO). KO contained the highest level of saturates (SFA; 39%) and monounsaturates (MUFA; 38%), and was low in polyunsaturated fatty acids (PUFA; 24%) compared to CO (50%) and FO (43%). CO and FO contained lower levels of SFA (31% and 33%, respectively) and MUFA (19% and 24%, respectively). Lipid digestibility of the CO diet (81%) was significantly lower than that of KO (90%) and FO (93%) diets (P < 0.05), likely due to wax esters in CO. Digestibility of SFA in the CO diet (70%) was significantly lower than FO (75%) and KO (77%) and MUFA in CO (84%) was significantly lower than KO (93%) and FO (93%). Digestibility of PUFA was significantly higher in FO (97%) than CO (94%) and KO (95%). Generally the CO diet was significantly less digestible than FO and KO diets.