Exploring alternative oils for extruded aquafeed

The rapid intensification of aquaculture has increased reliance on the commercial aquafeed sector. While aquaculture is critical to mitigate global deficits in ω-3-rich seafood driven by the overexploitation of wild fisheries, the industry is constrained by its overdependence on wild-harvested fish oil and plant oils, e.g. soybean, for dietary lipid inputs. Most vegetable oils lack sufficient ω-3 poly-unsaturated fatty acids (PUFAs) while containing high levels of ω-6 PUFAs, which can ultimately impede optimal fish growth and performance. This study, part of the Circolie project, evaluated the lipid characterization, oxidative stability, physico-chemical characterization of alternative oils of plant and animal origin to replace fish oil in salmonid formulations. Lipid profiling revealed that all samples except microalgae surpassed fish oil in linoleic acid (18:2ω6, LA) while camelina, salmon, and linseed oils provided superior α-linolenic acid (18:3ω3, ALA) levels. Camelina (1.5%) and microalgae (3.2%) were rich in eicosatrienoic acid (20:3ω3, ETA), a key intermediate in the biosynthesis of long chain PUFAs. Microalgae oil also outperformed fish oil in eicosapentaenoic acid (C20:5ω3,

EPA) and docosahexaenoic acid (C22:6ω3, DHA) , establishing camelina, linseed, and microalgae as viable fish oil replacers. To balance nutritional demands (20% - 40% metabolic energy; 1% - 2.5% dietary DHA/EPA) , cost and circularity, black soldier fly, poultry, and pork fats were selected for blending. Thermal and rheological analyses showed that applying fully molten oils (>40ºC) during vacuum coating eliminates yield stress, preventing nozzle blockage and maximizing coating efficiency. Finally, blending decreased solid fat content, following a dilution effect, which might lead to increased oil leakage.