Effects of Dietary Lipid Source on Growth, Survival, and Fatty Acid Composition of Brown Trout Juveniles, Salmo trutta

An eight-week feeding trial was conducted to investigate the suitability of vegetable and animal oils as total replacements for cod liver oil in feeds for brown trout juveniles. Four isonitrogenous (65%) and isolipidic (15%) diets were formulated containing cod liver oil, soybean oil, goose fat, or mixed-fat (blend). Growth performance and survival did not significantly differ among treatments. Fatty acids in the neutral and phospholipid fractions of the fish generally reflected the fatty acid composition of the dietary lipid source. Palmitic (16: 0) and oleic acid (18: 1 n-9) were the major saturated and monounsaturated fatty acids in the neutral and phospholipid fractions of the fish. The highest total n-6 polyunsaturated fatty acid (n-6 PUFA) was obtained in fish fed the soybean oil diet. The highest eicosapentaenoic acid (EPA, 20: 5 n-3), docosahexaenoic acid (DHA, 22: 6 n-3), total n-3 PUFA, and n-3/n-6 PUFA ratio were obtained in fish fed the cod liver oil diet (p < 0.05). Results suggest that fish oil can be totally replaced by soybean oil and goose fat without negative effects on growth performance or survival but further trials with longer feeding periods and fish with weights closer to commercial size are required to evaluate the n-3 highly unsaturated fatty acid (HUFA) level in the muscle.