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 ei ther 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 obta ined from head kidney and the fatty acid compositions of the individua l membrane phospholipids measured. In general phospholipids from SO- a nd LO-fed fish had increased 18:2(n-6), 20:2(n-6) and 20:3(n-6) compar ed to the fish oil treatments while LO-fed fish had lower 20:4(n-6) th an 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 kidne y macrophage-enriched leucocyte phospholipids was highest in MO-fed fi sh followed by FO- and LO-fed fish with the lowest level in fish fed S O. 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 L O. Production of LTB(5) by kidney macrophage-enriched leucocytes stimu lated with A23187 was highest in MO-fed fish and lowest in those fed S O. Production of LTB, was greatest in SO-fed fish and lowest in fish f ed LO. Serum Ig levels were significantly affected by dietary treatmen t with highest values in fish fed FO and SO and lowest in fish fed MO and LO.