Effect of dietary lipid level on growth performance and feed utilization by European sea bass juveniles (Dicentrarchus labrax)

A study was undertaken to determine the effect of the dietary lipid level on growth and feed efficiency of European sea bass juveniles. Four isonitrogenous diets (48% crude protein) with increasing dietary lipid levels (12, 18, 24 and 30% DM) were fed to satiety to triplicate groups of 25 fish (IBW = 7 g) for 8 weeks. Final body weight of fish fed the 24% lipid diet was significantly higher than that of fish fed the 12 and 30% lipid diets, although no significant differences in SGR were observed among groups. Feed efficiency values for the 30% lipid diet were significantly lower than those for the other diets. Feed intake of the 12, 18 and 24% lipid diets seemed to be regulated more by protein intake rather than by energy intake. With the 30% lipid diet, both protein and energy intake (g kg(-1) day(-1)) were significantly higher than with the other diets. At the end of growth trial, protein content was significantly higher in fish fed the 12% lipid diet, and lipid and energy content were significantly lower in fish fed the 12 and 18% lipid diets than in the other groups. Liver lipid content was significantly higher in fish fed the 24% lipid diet than in the other groups. Muscle lipid content was unaffected by dietary lipid level. Nitrogen and energy retention (percentage intake) values were significantly lower in fish fed the 30% lipid diet than in the other groups. Energy retention (percentage intake) increased as dietary lipid level increased from 12 to 24%. Lipid retention (percentage intake) decreased as dietary lipid level increased. The apparent digestibility coefficients (ADC) of dry matter and protein were not affected by diet composition, while ADC of lipid and energy were significantly higher in the 24 and 30% lipid diets. The results of this trial indicate that an increase of dietary lipid level from 12 to 24% did not improve growth performance and feed efficiency of sea bass juveniles. The increase of dietary lipid level had no protein sparing effect. Although, the inclusion of 30% of dietary lipid did not depress growth rate, it significantly reduced protein and energy retention efficiencies. It may be concluded that, under the experimental conditions, the increase of dietary lipid level beyond 12% had no beneficial effects.