title: Long-term feeding of Atlantic salmon in seawater with low dietary long-chain n-3 fatty acids affects tissue status of the brain, retina and erythrocytes.
abstract: In two long-term feeding trials in seawater, Atlantic salmon were fed EPA+DHA in graded levels, from 1·3 to 7·4 % of fatty acids (FA, 4-24 g/kg feed) combined with approximately 10 % 18 : 3n-3, at 6 and 12°C. Dietary EPA appeared to be sufficient in all diet groups, as no differences were seen in polar lipid tissue concentrations of either the brain, retina or erythrocytes. For DHA, a reduction in tissue levels was observed with low dietary supply. Effects on brain DHA at ≤1·4 % EPA+DHA of dietary FA and retina DHA at ≤2·7 % EPA+DHA of dietary FA were only observed in fish reared at 6°C, suggesting an effect of temperature, whereas tissue levels of n-6 FA increased as a response to increased dietary n-6 FA in both the brain and the retina at both temperatures. DHA levels in erythrocytes were affected by ≤2·7 % EPA+DHA at both temperatures. Therefore, DHA appears to be the limiting n-3 FA in diets where EPA and DHA are present in the ratios found in fishmeal and fish oil. To assess the physiological significance of FA differences in erythrocytes, the osmotic resistance was tested, but it did not vary between dietary groups. In conclusion, ≤2·7 % EPA+DHA of FA (≤9 g/kg feed) is not sufficient to maintain tissue DHA status in important tissues of Atlantic salmon throughout the seawater production cycle despite the presence of dietary 18 : 3n-3, and effects may be more severe at low water temperatures.
authors.affiliation: 1National Institute of Seafood and Nutrition Research (NIFES),Postboks 2029,Nordnes, 5817 Bergen,Norway.
authors.forename: N H
authors.initials: NH
authors.lastname: Sissener
authors.affiliation: 1National Institute of Seafood and Nutrition Research (NIFES),Postboks 2029,Nordnes, 5817 Bergen,Norway.
authors.forename: B E
authors.initials: BE
authors.lastname: Torstensen
authors.affiliation: 2Skretting ARC,Sjøhagen 3,4016 Stavanger,Norway.
authors.forename: I
authors.initials: I
authors.lastname: Stubhaug
authors.affiliation: 2Skretting ARC,Sjøhagen 3,4016 Stavanger,Norway.
authors.forename: G
authors.initials: G
authors.lastname: Rosenlund
mesh_terms: D000821:Animal Feed; D000824:Animal Nutritional Physiological Phenomena; D000818:Animals; D017756:Aquaculture; D001921:Brain / Q000378:metabolism*; D004032:Diet; D004281:Docosahexaenoic Acids / Q000008:administration & dosage / Q000378:metabolism; D015118:Eicosapentaenoic Acid / Q000008:administration & dosage / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D015525:Fatty Acids, Omega-3 / Q000008:administration & dosage / Q000378:metabolism*; D012160:Retina / Q000378:metabolism*; D020317:Salmo salar / Q000378:metabolism*; D012623:Seawater; D013696:Temperature
chemical_list: D015525:Fatty Acids, Omega-3; D004281:Docosahexaenoic Acids; D015118:Eicosapentaenoic Acid
keywords: ARA arachidonic acid; Atlantic salmon; Brain; DHA; EFA essential fatty acid; EPA; Erythrocytes; FA fatty acid; FM fishmeal; FO fish oil; LNA 
                    α linolenic acid; NL neutral lipids; PL polar lipids; Requirements; Retina