Optimum protein-to-energy ratio for two size groups of rabbitfish, Siganus canaliculatus (Park)

Three approximately isoenergetic (17 kJ g^?1) diets were formulated with dietary protein levels of 270, 360 and 480 g kg^?1 (DM basis) providing protein-to-energy ratios of 15.69, 20.48 and 27.16 mg crude protein (CP) kJ^?1, respectively. The effects of these diets on several growth and nutritional parameters were evaluated for the fry (2.50 ± 0.184 g) and fingerlings (11.53 ± 0.023 g) of Siganus canaliculatus (Park). Maximum growth and best feed utilization efficiency of fry were obtained using the diet containing 480 g kg^?1 protein and P:E ratio of 27.16 mg CP kJ^?1. For fingerlings the best results were obtained with the diet containing 360 g kg^?1 protein and P:E ratio of 20.48 mg CP kJ. Body composition of the fry was not affected by the feeding regime whilst the effect was evident in the fingerling groups. The carcass protein content of the fingerling was observed to increase with increasing P:E ratios while lipid content decreased as P:E increased.