Growth, feed utilization and body lipid content of gilthead seabream ( Sparus aurata) fed increasing lipid levels and fish meals of different quality

Abstract

The present study shows the effects of feeding gilthead seabream, 70 to 400 g, with nine diets containing three different lipid levels (15, 22 and 28% on a dry weight basis), combined with two types of fish meal of different quality. In addition, feed processing effects (extruded vs. pelletized) were also compared for the diet containing 22% lipid. The diets prepared with the high quality fish meal promoted better growth than those prepared with the low quality one. Protein utilization was enhanced by a sparing effect of dietary lipid at 22%. This lipid level needed to be increased up to 28% with low quality meal to effectively spare dietary protein. A significant increase in fish growth with higher dietary lipid levels, in both high and low quality fish meal diets, was only related to a significant increase in total body lipid content in high quality fish meal diets, and an excess of lipid may have been the cause of hepatocyte abnormalities in fish fed the highest lipid levels. The effect of pellet processing was apparent in low quality fish meal diets, where a significantly better growth performance was obtained in fish fed the extruded diet. There were no significant differences among all treatments in feed intake, and values were similar to those suggested by commercial fish feed producers, for similar fish size and water temperatures. Values for feed conversion ratio (FCR) were lower than 1.6 for all diets.