Effects on performance and product quality in Atlantic salmon fed diets reduced in organic pollutants

Jan Olli¹, Bente Ruyter², Turid Mørkøre^2, Harald Breivik³, Aimo Oikari⁵, Aleksei Krasnov², Olav Thorstad⁴, Åshild Krogdahl⁶ , Gunnar Berge⁸ and Torbjørn Åsgård^7*

¹ AVS Chile SA, Casilla 300, Puerto Varas, Chile

² The Norwegian Institute of Food, Fisheries and Aquaculture Research (Nofima), P.O. Box 5010, NO-1432 Ås, Norway

³Neperdo™ Biomarine, Porsgrunn, Norway

⁴ Pronova,BioPharma P.O Box 2109, NO-3202 Sandefjord, Norway

⁵University of Jyväskylä, , P.O.Box 35, FIN-40014 Jyväskylän yliopistoy

⁶Norwegian School of Veterinary Science, Oslo, Norway.

 ⁸Pronova,BioPharma P.O.Box 420, 1327 Lysaer, Norway.⁷ The Norwegian Institute of Food, Fisheries and Aquaculture Research (Nofima), NO-6600 Sunndalsøra, Norway

Oily fish, including Atlantic salmon, due to their content of omega-3 fatty acids, are considered healthy for human consumption. However, marine raw materials used in fish diets are considered a major source of persistent organic environmental pollutants (POPs). Advice regarding fish consumption has therefore been complicated by reports that some species are burdened with potentially harmful levels of POPs, such as dioxins, PCBs and brominated flame retardants (BFRs). Despite the rather low levels of environmental pollutants found in farmed Atlantic salmon, there is still some concern about the levels found. One should therefore aim at reducing the level of POPs in aquacultured fish, in order to strengthen the “healthy image” of the product. As a way to reduce these POPs in farmed fish, Pronova

BioPharma Norge AS has developed a short path distillation process using a volatile working fluid efficiently removing POPs from fish oils. Potential beneficial effects in the farmed fish from reducing the POPs in the feed oil, were tested in a study lasting from post smolt size to slaughter size at Gildeskål Research Station (GIFAS), Norway. The fish were given feeds containing purified or not purified fish oil, four replicates per treatment. The effects on growth, health and fillet quality were studied. There was a tendency for better growth and feed utilisation in the group receiving feed containing purified oil. This was particularly the case during periods of high growth when both the growth rate and feed utilisation rate were significantly better for the fish that received the feed containing purified oil. The salmon that received the feed containing purified oil appeared to better tackle the handling stress during the slaughtering process, measured as a delayed pH reduction after killing. Other stress markers showed the same tendencies. All the fish in the trial maintained a good red colour and firmness, but there was a tendency that fish that received the feed containing purified oil had a firmer texture. The difference in texture was most pronounced after freezing. The proportion of salmon with soft texture was then halved in comparison to the fish that received unpurified oil.