Protein sparing effect of dietary lipids in common dentex (Dentex dentex):a comparative study with sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax)

The common dentex (Dentex dentex) is a sparid fish which is considered a su itable candidate for Mediterranean aquaculture. A seven-weeks feeding trial was conducted over the summer period with common dentex, sea bream (Sparus aurata) and sea bass (Dicentrarchus labrax). All three species were fed to visual satiety with two practical diets with varying crude protein and cru de fat levels (55 % protein, 9 % lipids; 46 % protein, 17 % lipids). The in itial body weights were 8.2, 11.6 and 17.3 g for common dentex, sea bass an d sea bream, respectively. In all cases, specific growth rates were not sig nificantly affected by dietary treatment, but they varied among species (se a bass 1.7-1.8 %; sea bream 2.1-2.3 %; common dentex 3.1-3.2 %). When compa risons between fish species were made, we observed that the increase in gro wth rates was linked to a decrease of the whole body fat content, as a cons equence of a greater utilisation of dietary lipids as energy substrates. Fu rthermore, in common dentex, the 17 % lipid diet was able to improve protei n retention, but this diet effect was less significant in sea bream and sea bass. In contrast to sea bream, the 17 % lipid diet did not up-regulate pl asma GH levels in common dentex, which provides additional evidence for a m ore efficient utilisation of dietary lipids. (C) Ifremer/Elsevier, Paris.