Growth performance, feed utilization and body composition of Dentex dentex fed on different macronutrient combinations.

Determining an adequate macronutrient balance is essential to guarantee the production success. As protein is the limiting component for ¢sh food, the utilization of lipids or carbohydrates as partial substitutes of this nutrient is a challenge to improve its use. In order to get an approximation of the maximum levels of utilization for carbohydrates and/or lipids and determine themost adequatemacronutrient to partly replace protein as the main energy source of diets for dentex (91.7 ± 1.4 g mean weight), four experimental diets with different protein:lipid:carbohydrate percentages (43/16/28, 43/24/4, 38/19/28 and 38/24/13) were tested for 13 weeks. The results indicated the possibility of using 38% of dietary proteinwithout affecting growth performance, under the experimental conditions. There were no di¡erences among the four diets either in most of the nutritive utilization indicators or in the body composition and haematological parameters. The influence of dietary composition was only observed in the feed intake, being higher with more dietary carbohydrates, and the hepatosomatic index and protein e?ciency ratio, showing more elevated values in diets with a higher lipid level. The dentex capacity of using both carbohydrates and lipids e?ciently to obtain the necessary energy for its correct growth, as well as to compensate the energetic ‘vacuum’ caused by the dietary protein reduction, under the assayed conditions, was con¢rmed.