Complete replacement of fish oil with a blend of vegetable oils affects dioxin, dioxin-like polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in 3 Atlantic salmon ( Salmo salar) families differing in flesh adiposity

Abstract

The benefits of consuming a diet rich in seafood are now well respected and are based not only on the high levels of long-chain n−3 polyunsaturated fatty acids (LC n−3 PUFA) but also due to the range of beneficial macro and micronutrients present in fish. Atlantic salmon culture is now established globally and is a major source of high-quality oil rich in LC n−3 PUFA. However, salmon flesh can accumulate persistent organic pollutants (POPs), including dioxins and furans (PCDD/Fs), dioxin-like polychlorinated biphenyls (DL-PCBs) and polybrominated diphenyl ethers (PBDEs) that are derived from marine feed components, especially fish oil (FO). The aim of this study was to grow salmon smolts on alternative diets with a reduced FM level, that contained either 100% of added oil as FO or a blend of vegetable oils (VO), over a full production cycle and to assess the effects of these diets on POP deposition. Three families of salmon were used with two being chosen as being either “Lean” or “Fat”, based on flesh adiposity derived from a breeding programme, while the third (CAL) was a mix of non-pedigreed commercial families. Fish were ongrown for 55 weeks when they reached 3 kg followed by a switch to a decontaminated FO for a further 24 weeks to restore LC n−3 PUFA levels in the VO-fed fish. The average sum flesh PCDD/Fs, across the 3 salmon strains, were reduced from 1.94 ± 0.01 ng TEQ/kg in the fish fed FO to 0.46 ± 0.02 ng TEQ/kg in the fish fed VO. The sum PBDEs were reduced from 2.82 ± 0.24 ng/g in the FO fish to 0.52 ng/g in the VO fish. Average reduction in sum PCDD/Fs, DL-PCBs and PBDEs was 52, 79 and 82%, respectively, in the VO fed salmon. There was evidence of higher PBDE retention in the Fat fish but this was not significant. This study shows that salmon can be produced with very low levels of POPs and that concentrations can be reduced significantly by the careful selection of raw materials. The use of decontaminated fish oils has an important role in this process although care should be taken to use oils that are treated with protocols that reduce PCCD/Fs, DL-PCBs and PBDEs to ensure very low levels of POPs in commercial salmon.