Feed formulations based on energy and protein demands in white grouper (Epinephelus aeneus)

White grouper a Mediterranean species, is a new promising candidate for Israeli mariculture. In order to develop feeds that promote the most efficient growth and cause low environmental impact the requirements of grouper for key nutrients have been quantified. Daily requirements for energy and protein were determined as the sum of maintenance and growth and the efficiencies for energy and protein deposition were estimated according to the following approach: Requirement = a × BW (kg)b + c × gain; BW (kg)b = Metabolic body weight; a = maintenance requirement; c = coefficient describing the efficiency of utilization of dietary energy or protein for growth. The daily weight gain as a function of body weight (g) and temperature (°C) was predicted by the equation: y = 0.062 × BW (g)0.558 × exp0.030 × Temp. The composition of the gain was measured by analyzing whole fish ranging from 1 to 1600 g. The energy content was dependent upon fish weight and increased from 4.8 to 7.5 kJ g− 1 body mass, whereas the protein content remained constant at 169 mg g− 1. The efficiencies of utilization of digestible energy (DE) and digestible protein (DP) for maintenance and growth in white grouper were determined by feeding fish of various sizes at increasing levels from zero to maximum voluntary feed intake, as well as three different water temperature regimes. Maintenance requirement for energy and protein increased with increasing temperatures. The relationships between DE intake and energy gain as well as DP intake and protein gain were found to be linear throughout and were both independent of feed intake, body weight and temperature. Daily requirements of white grouper at 24 °C can be thus calculated as follows: Digestible energy need (kJ fish− 1 day− 1) = 40.7 × BW (kg)0.80 + 1.52 × energy gain; Digestible protein need (g fish− 1 day− 1) = 0.39 × BW (kg)0.70 + 1.85 × protein gain. Based on those results, feeds can be formulated for white grouper with optimal energy to protein ratio during the entire grow-out period to increase retention efficiency and reduce excretion of nutrients.