Abstract
Gilthead bream ( Sparus aurata) of 1 g mean weight were fed six purified diets supplemented with 12% lipid composed of different proportions of soybean oil (SBO) and cod-liver cil (CLO). The experiment lasted for 5 months. Fish performance and body composition, as well as the fatty acid composition of liver phospholipids, were studied. Fish performance improved with increasing dietary CLO content, approaching an optimum at about 6% CLO. Higher values for liver fat content and hepatosomatic index were observed for diets containing less than 6% CLO suggesting a deficiency of essential fatty acids in these diets. Liver fatty infiltration with low CLO diets was high although a certain degree of fatty infiltration was apparent in livers of all the dietary treatments. Body composition of fish was also affected by dietary lipid composition. Higher protein and lower fat contents were observed for the fish fed low levels of CLO. The eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) content of liver phospholipids was high, approaching a constant value after inclusion of 6% CLO. The levels of 20:4 n − 6 were also found to approach a plateau at this level. Saturated and n − 9 fatty acid content remained almost stable, while the level of 18:2 n − 6 in liver phospholipids reflected the amount of SBO in the diet. It is concluded that, under the conditions employed, the minimum requirement of gilthead bream for EPA and DHA is around 0.9% of the diet.
Published Version
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