Fat powder can be a feasible lipid source in aquafeed for the carnivorous marine teleost golden pompano, Trachinotus ovatus

Abstract

In the production of aquafeeds, exogenous liquid oils are usually added directly or by vacuum coating. In order to evaluate the practicality of fat powder in aquafeeds and aquaculture, four isoproteic (46%) and isolipidic (12%) diets named FOl, BOl, FOp, and BOp were prepared with fish oil (FO) or blend oil (BO, consisting of fish, soybean, rapeseed, and perilla oils) or their corresponding fat powder as dietary lipid, respectively. Each diet was fed to triplicate groups of golden pompano Trachinotus ovatus juveniles (initial body weight about 15.10 g) in floating sea cages (1.0 × 1.0 × 2.0 m, 30 fish per cage) for 10 weeks. Fish were fed to nearly satiation at two times each day. The results showed that the final weight, weight gain rate (WGR), specific growth rate (SGR), food conversion ratio (FCR), condition factor (CF), viscerosomatic index (VSI), and survival rate (SUR) displayed no significant difference among the four dietary groups (P > 0.05), while the hepatosomatic index (HSI) in the BOp group (1.01) was significantly lower than that in FO-base groups (1.19–1.23) (P < 0.05). The fatty acid (FA) composition in livers or dorsal muscle showed no difference between the fish fed the diets from liquid oil and corresponding fat powder. A significantly high serum alkaline phosphatase (ALP) activity and low hepatic malondialdehyde (MDA) level were detected in the BOp group (P < 0.05). Moreover, the mRNA levels of hepatic glutathione peroxidase (gsh-px), superoxide dismutase (sod), and catalase (cat), as well as intestinal FA binding protein 2 (fabp2) and FA transport protein 4 (fatp4) genes in one or both of the fat powder groups, were significantly higher than those in the corresponding liquid oil groups (P < 0.05). Additionally, the peroxide value (POV) and MDA level in FOp and BOp diets were less than 27% of those in FOl and BOl diets after stored at − 20 °C for 3 months. These results demonstrated that fat powder diets, especially BOp, displayed better effects than liquid oil diets in lipid oxidation stability, liver health, and FA transportation in T. ovatus, which indicated that fat powder can be a feasible lipid source in aquafeed. To our knowledge, this is the first report on the practical application of fat powder in aquaculture, which may provide a new form of lipid addition in the aquafeeds industry.