Full replacement of fish oil with algae oil in farmed Atlantic salmon (Salmo salar) – Debottlenecking omega 3

Abstract

The global goal of developing sustainable aquafeed has faced increased complexity in sourcing raw materials. The limited availability of fish oil (FO) is a well-known bottleneck for the aquaculture industry and pairing it with EFSA (EFSA CONTAM, 2018) reduced tolerable weekly intake of marine contaminants [polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) and dioxin-like polychlorinated biphenyls (DLPCB)] creates another challenge for wild caught FO and its use in fish feed. In recent years, commercial algal alternatives have increasingly become available. Not only would omega-3 sources from algae reduce the reliance on FO; it would allow for restoration of the long chain omega-3 levels in farmed salmon. To this end, a study was conducted to establish knowledge on full replacement of FO by algae oil (Schizochytrium sp.) in Atlantic salmon with the aim of reducing contaminants levels in the fillet and maintaining the level of omega-3 fatty acid (FA), growth performance, health, and final product quality. Atlantic salmon (531 g) were distributed into twelve 5 × 5 × 5 m sea cages and fed one of four diets for 369 days: a control diet (Control) containing FO + rapeseed oil (VO1); a diet where AlgaPrime (AP) replaced 50% of the sum of EPA + DHA from FO (50AP + VO1); a diet where AP replaced 100% of the sum of EPA + DHA from FO (100AP + VO1), and a diet the same as the previous but using linseed instead of rapeseed oil (VO2; 100AP + VO2). All diets were balanced for key micronutrients. At the end of the trial, zootechnical parameters were obtained, health and welfare assessed, and final fillet quality analysed for contaminants and fillet quality post slaughter. Full replacement of FO significantly reduced the levels of PCDD/F and DLPCB in the fillet of 4 kg salmon by 70% and 79% respectively for 100AP + VO1 and 40% and 43% respectively for 100AP + VO2 fed fish. Fish gained an average of 3.7 kg across treatments (average final weight 4235.8 g ± 191.8); almost an 8-fold increase for all treatments. No significant differences were found among diets for performance, feed intake, gut health, histology, welfare, pigmentation, or fillet quality. This study demonstrates that AlgaPrime can be used to fully replace FO in Atlantic salmon grower feed without negative effects, achieving an important impact on food safety and sustainability for aquafeed producers and salmon consumers.