Comparison of energy and protein efficiency among three fish species gilthead sea bream (Sparus aurata), European sea bass (Dicentrarchus labrax) and white grouper (Epinephelus aeneus):: energy expenditure for protein and lipid deposition

This study was carried out in order to compare the daily energy needs in three fish species: gilthead sea bream, European sea bass and white grouper. The requirements for maintenance and growth and the efficiencies for protein and lipid deposition were estimated. The energy requirement for maintenance is proportional to the metabolic body weight in the form of a x BW(kg)(b), whereas the requirement for growth is dependent on the amount and the composition of the added tissue. The exponent b of the metabolic body weight was determined by energy loss during starvation using fish ranging from 1 to 400 g. Similar values of 0.82, 0.80 and 0.79 were determined for the three species. The efficiencies of digestible energy for growth were determined by feeding fish at increasing levels, starting at zero and up to close to maximum voluntary feed intake. Digestible energy intake and the subsequent energy gain partitioned into protein and lipid gain were measured by comparative slaughter technique. Plotting the relationships (x = DE intake, y = energy gain) for each fish species, the resulting equations proved to be linear throughout, defining the efficiency of utilization of energy by the value of the slope. As the energy gain consists of protein, as well as lipid energy, a multiple regression was employed to determine the energy coefficients for protein and lipid deposition simultaneously with the maintenance requirement: DE intake (kJ) = DEmaint + 1/k(p) x protein energy (kJ) + 1/k(L) x lipid energy (kJ). The calculated energy cost for protein gain (1/k(p)) ranged from 1.79 to 1.90 kJ per kJ protein energy deposited. Energy cost (1/k(L)) for lipid gain was lower than the energy cost for protein gain and ranged from 1.10 to 1.31 kJ per kJ lipid deposited. Therefore, we conclude that utilization of energy and protein for growth does not appear to be very different across the species examined. Differences were found, however, in the magnitude and the composition of the weight gain, which ultimately determines the amount of energy and protein required. (C) 2003 Elsevier Science B.V. All rights reserved.