EFFECTS OF DIETARY BORAGE OIL [ENRICHED IN GAMMA-LINOLENIC ACID, 18 3(N-6)] OR MARINE FISH-OIL [ENRICHED IN EICOSAPENTAENOIC ACID, 20/5(N-3)] ON GROWTH, MORTALITIES, LIVER HISTOPATHOLOGY AND LIPID-COMPOSITION OF JUVENILE TURBOT (SCOPHTHALMUS-MAXIMUS)/

A marine fish oil, Marinol K (MO) and borage oil (BO) were used to for mulate diets relatively rich in eicosapentaenoic acid [EPA; 20:5(n-3)] and gamma-linolenic acid [GLA; 18:3(n-6)], respectively. The diets we re fed to duplicate groups of juvenile turbot (Scophthalmus maximus) o f initial weight 1.4 g for a period of 12 weeks. No differences were o bserved in final weights either between duplicate tanks or between die tary treatments. Mortalities in the MO-fed group were significantly gr eater than in the BO-fed group. In the MO-fed group, 7 out of 12 fish sampled for histological analysis showed a pronounced liver histopatho logy whereas only 1 of 12 fish sampled in the BO-fed group showed slig ht pathology. EPA levels were increased 2.2-fold and its elongation pr oduct, 22:5(n-3), was increased 1.8-fold while arachidonic acid [AA; 2 0:4(n-6)] was decreased by 30% in MO-fed fish compared to the initial carcass composition. GLA was increased 53-fold and its elongation prod uct dihomo-gamma-linolenic acid [DHGLA; 20:3(n-6)] was increased 16-fo ld while AA was reduced by 90% in BO-fed fish compared to the initial carcass composition. The amount of triacylglycerol in liver of BO-fed fish was significantly greater than levels in MO-fed fish. The fatty a cid compositions of individual phospholipids from liver showed marked differences between dietary treatments. Fish fed MO had significantly higher levels of the (n-3) polyunsaturated fatty acids (PUFA), 20:5(n- 3), 22:5(n-3) and 22:6(n-3), and also significantly more 20:4(n-6) com pared to BO-fed fish which had significantly higher 18:2(n-6), 18:3(n- 6), 20:2(n-6) and 20:3(n-6). The composition of liver phosphatidylinos itol was particularly unusual in BO-fed fish having DHGLA as the major C-20 PUFA which was 2.2-fold greater than AA and 3.9-fold greater tha n EPA. This study demonstrates that the carcass composition of turbot can be altered, by means of dietary lipids, to contain increased level s of EPA and DHGLA which would be of potential benefit in human as wel l as in fish nutrition. However, caution should be exercised when usin g very highly unsaturated oils relatively rich in EPA which may genera te histopathological lesions in the fish.