Dietary choline requirement for juvenile cobia, Rachycentron canadum

A 10-wk feeding trial was conducted to determine dietary choline requirement for juvenile cobia. The basal diet was formulated to contain 47.1 g crude protein 100 g− 1 dry weight from vitamin-free casein, gelatin and fish protein concentrate. This premix provided methionine at 1.05%, slightly less than the optimal requirement of cobia (1.19%), so endogenous synthesis of choline from methionine would be limited. Choline chloride was supplemented to the basal diet to formulate six purified diets containing 133 (control group), 350, 548, 940, 2017 and 3981 mg choline kg− 1 diet, respectively. Each diet was randomly fed to triplicate groups of juvenile cobia with initial average weight 4.2 ± 0.4 g in a flow-through system. Dietary choline level significantly influenced survival, feeding rate, weight gain, feed efficiency ratio, hepatosomatic index, as well as the choline concentrations in the liver and muscle of cobia. Broke-line regression of weight gain, liver and muscle choline concentration yield choline requirements of 696, 877 and 950 mg choline kg− 1 diet in the form of choline chloride, respectively. In addition, dietary choline supplementation significantly increased muscle lipid content of cobia. Potential manipulation of muscle lipid and associated flavor and texture by choline supplementation warrants further investigation.