Dietary lipid affects phospholipid fatty acid compositions, eicosanoid production and immune function in Atlantic salmon (Salmo salar)

Atlantic salmon (Salmo salar) post-smelts were fed diets containing either Fosol (FO), a North Sea fish oil, sunflower oil (SO), linseed oil (LO) or Marinol K (MO), a southern hemisphere fish oil rich in 20:5(n-3) for 12 weeks. A macrophage-enriched leucocyte preparation was obtained from head kidney and the fatty acid compositions of the individual membrane phospholipids measured. In general phospholipids from SO- and LO-fed fish had increased 18:2(n-6), 20:2(n-6) and 20:3(n-6) compared to the fish oil treatments while LO-fed fish had lower 20:4(n-6) than any other dietary treatment. Fish fed LO also had increased 18:3(n-3), 18:4(n-3), 20:3(n-3) and 20:4(n-3). The 20:5(n-3) content of kidney macrophage-enriched leucocyte phospholipids was highest in MO-fed fish followed by FO- and LO-fed fish with the lowest level in fish fed SO. The overall effect on the ratio of eicosanoid precursors, 20:4/20:5, showed the highest value in SO-fed fish and the lowest in fish fed LO. Production of LTB(5) by kidney macrophage-enriched leucocytes stimulated with A23187 was highest in MO-fed fish and lowest in those fed SO. Production of LTB, was greatest in SO-fed fish and lowest in fish fed LO. Serum Ig levels were significantly affected by dietary treatment with highest values in fish fed FO and SO and lowest in fish fed MO and LO.