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

Abstract

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 FAE d, FAE p and FAE e, respectively, but all of the variations were small. Relationships between specific growth rate in wet weight (SGR w, % per day), dry weight (SGR d, % per day), protein (SGR p, % per day), energy (SGR e, % per day) and ration level (RL, % per day) were linear and described as simple equations SGR w = 0.738RL–0.764, SGR d = 0.871RL–0.928, SGR p = 0.904RL–0.966 and SGR e = 1.038RL–1.060. Feed conversion efficiency in wet weight (FCE w, %), dry weight (FCE d, %), protein (FCE p, %) and energy (FCE e, %) all increased as ration increased and maximized at ad libitum ration level. Energy budgets of juvenile Epinephelus awoara at satiation ration level was: 100 C = 2 F + 4 U + 75 R + 19 G or 100 A = 80 R + 20 G, 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.