EFFECT OF DIFFERENT LEVELS OF N-3 HIGHLY UNSATURATED FATTY-ACIDS ON GROWTH AND FATTY-ACID COMPOSITION OF JUVENILE GILTHEAD SEABREAM (SPARUS-AURATA)

The requirements of juvenile gilthead seabream for n-3 highly unsaturated fatty acids (n-3 HUFA) were studied by feeding fish with diets containing 4 different levels of n-3 HUFA ranging from 0.76 to 2.94% of the diet. Juvenile fish weighing 42.5 +/- 0.21 g were randomly divided into 12 groups of 15 fish and pair fed the 4 experimental diets for 8 weeks. No mortality was observed during the feeding trial, but significant differences were found in growth rate and biochemical composition of the fish. Fish fed low dietary n-3 HUFA (0.76% of the diet) showed poor growth rates and low feed efficiency ratios, but these parameters improved by the elevation of the n-3 HUFA levels in the diet up to 1.9%. Fish fed the lowest n-3 HUFA diet showed the highest levels of crude lipid in the liver and gills. Muscle and gill phospholipids were generally less influenced by the type of diet than the liver. Results of this experiment suggest that with dietary lipid contents of 8-10%, the requirements for essential fatty acids of juvenile gilthead seabream is about 1.9% n-3 HUFA of the dry diet.