Effects of dietary lipid level and vegetable oil on fatty acid metabolism in Atlantic salmon (Salmo salar L.) over the whole production cycle |
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Authors: | DR Tocher JG Bell F McGhee JR Dick J Fonseca-Madrigal |
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Institution: | (1) Institute of Aquaculture, University of Stirling, Stirling FK9 4LA, Scotland, UK |
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Abstract: | Changes in fatty acid metabolism in Atlantic salmon (Salmo salar) induced by vegetable oil (VO) replacement of fish oil (FO) and high dietary oil in aquaculture diets can have negative impacts
on the nutritional quality of the product for the human consumer, including altered flesh fatty acid composition and lipid
content. A dietary trial was designed to investigate the twin problems of FO replacement and high energy diets in salmon throughout
the entire production cycle. Salmon were grown from first feeding to around 2 kg on diets in which FO was completely replaced
by a 1:1 blend of linseed and rapeseed oils at low (14–17%) and high (25–35%) dietary oil levels. This paper reports specifically
on the influence of diet on various aspects of fatty acid metabolism. Fatty acid compositions of liver, intestinal tissue
and gill were altered by the diets with increased proportions of C18 polyunsaturated fatty acids and decreased proportions of n-3 highly unsaturated fatty acids (HUFA) in fish fed VO compared
to fish fed FO. HUFA synthesis in hepatocytes and enterocytes was significantly higher in fish fed VO, whereas β-oxidation
was unaltered by either dietary oil content or type. Over the entire production cycle, HUFA synthesis in hepatocytes showed
a decreasing trend with age interrupted by a large peak in activity at seawater transfer. Gill cell prostaglandin (PG) production
showed a possible seasonal trend, with peak activities in winter and low activities in summer and at seawater transfer. PG
production in seawater was lower in fish fed the high oil diets with the lowest PG production generally observed in fish fed
high VO. The changes in fatty acid metabolism induced by high dietary oil and VO replacement contribute to altered flesh lipid
content and fatty acid compositions, and so merit continued investigation to minimize any negative impacts that sustainable,
environmentally-friendly and cost-effective aquaculture diets could have in the future.
Abbreviations: FO - fish oil; HUFA - highly unsaturated fatty acids acids (carbon chain length ≥C
20 with ≥3 double bonds); LO - linseed oil; RO - rapeseed oil; VO - vegetable oil.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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Keywords: | salmon fish oil vegetable oil dietary oil content HUFA synthesis β -oxidation prostaglandins |
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