Growth, faecal production, nitrogenous excretion and energy budget of juvenile yellow grouper (Epinephelus awoara) relative to ration level

Growth, faecal production, nitrogenous excretion and energy budget of juvenile yellow grouper (initial body weight 5.5 g or so) at various ration levels (starvation, 0.5%, 1% and 2% of initial body weight per day, and satiation) were investigated in this study. Faecal production (f, mg g− 1 d− 1) and nitrogenous excretion (u, mg g− 1 d− 1) increased markedly with increased ration level (RL, % per day), described as f = 0.483RL + 0.112 for faecal production and u = 0.218RL + 0.219 for nitrogenous excretion, respectively. Feed absorption efficiency (FAE, %) increased as ration increased with ranges of 91.4–94.0%, 95.6–97.3% and 96.5–97.6% for FAEd, FAEp and FAEe, respectively, but all of the variations were small. Relationships between specific growth rate in wet weight (SGRw, % per day), dry weight (SGRd, % per day), protein (SGRp, % per day), energy (SGRe, % per day) and ration level (RL, % per day) were linear and described as simple equations SGRw = 0.738RL–0.764, SGRd = 0.871RL–0.928, SGRp = 0.904RL–0.966 and SGRe = 1.038RL–1.060. Feed conversion efficiency in wet weight (FCEw, %), dry weight (FCEd, %), protein (FCEp, %) and energy (FCEe, %) all increased as ration increased and maximized at ad libitum ration level. Energy budgets of juvenile Epinephelus awoara at satiation ration level was: 100C = 2F + 4U + 75R + 19G or 100A = 80R + 20G, where C is food energy, A is assimilated energy, F is faeces energy, U is excretion energy, R is metabolism energy and G is growth energy.