Reducing the levels of dioxins and dioxin-like PCBs in farmed Atlantic salmon by substitution of fish oil with vegetable oil in the feed

• Published in: Aquaculture nutrition Vol. 11; no. 3; pp. 219 - 231
• Main Authors: Berntssen, M.H.G, Lundebye, A.K, Torstensen, B.E
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Science Ltd 01.06.2005
• Subjects: alternative oils; Atlantic salmon; bioaccumulation; body composition; dioxin-like polychlorinated biphenyls; dioxins; fatty acid composition; feed; feed composition; feed conversion; fish culture; fish farms; fish feeding; fish oils; food quality; lipid content; pelleted feeds; pollutants; polychlorinated dibenzodioxins; Salmo salar; salmon; vegetable oil; water pollution
• ISSN: 1353-5773; 1365-2095
• DOI: 10.1111/j.1365-2095.2005.00345.x

Atlantic salmon were fed extruded diets based on either 100% fish oil (FO) or 100% vegetable oil blend (VO) substitution for 22 months. A total of seven distinct feeding periods were studied that incorporated higher levels of dietary oil inclusion, and larger pellet size as fish size increased. Whole fish levels of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) and dioxin-like PCBs (DLPCB) were analysed at the beginning and end of each of the seven feeding periods. The PCDD/F and DLPCB concentrations in the FO diets increased from 2.43 to 4.74 ng WHO-TEQ kg(-1) (TEQ, toxic equivalents), while VO diets decreased from 1.07 to 0.33 WHO-TEQ kg(-1) as oil inclusion increased. Partial least square regression analyses identified feed concentration, growth rate and feed utilization, but not variations in lipid content, as factors significantly affecting fish PCDD/F and DLPCB levels. Accumulation efficiencies for DLPCB (740 +/- 90 g kg(-1)) were significantly (P < 0.01) higher than for PCDD/F (430 +/- 60 g kg(-1)), explaining the increasing dominance of DLPCB levels over PCDD/F levels in whole fish (DLPCB : PCDD/F ratio of 2.4 +/- 0.1 for both VO and FO fed fish) compared with feed (DLPCB : PCDD/F ratio of 1.5 and 0.34 for FO and VO feed respectively). Vegetable oil substitution significantly reduced the level of PCDD/F and DLPCB (eightfold and twelve-fold, respectively) in the fillet of a 2 kg salmon, but, also negatively affected beneficial health components such as fillet n-3/n-6 fatty acid ratio.