DIETARY VITAMIN K REQUIREMENTS OF JUVENILE GROUPER Epinephelus malabaricus

The study was aimed to evaluate the optimal dietary vitamin K requirements of juvenile grouper, Epinephelus malabaricus. Menadione sodium bisulfite was supplemented into a basal diet at 0, 1, 2, 5, 8, 12, 15 and 20 mg/kg diet, providing actual vitamin K concentration of 0, 0.98, 2.31, 5.31, 8.66, 12.05, 14.50 and 20.47 mg/kg diet, respectively. Total of 8 experimental diets were each fed to fed to triplicate groups of juvenile grouper (initial weight: 9.95 ± 0.05 g) in a recirculation rearing system for 8 weeks. Weight gain, feed efficiency and survival of grouper were not affected by the dietary treatments in this 8-weeks feeding trial. Fish fed the diet with 8.66 mg/kg diet had higher red blood cell count than fish fed the control diet. Total plasma prothrombin concentration was the highest in fish fed diets with ≥ 8.66 mg/kg diet, followed by fish fed the diet with 5.31 mg/kg diet, then fish fed diets with 2.31-5.31 mg/kg diet, and the lowest in fish fed the vitamin K-free control diet. Hepatic menaquinone-4 (MK-4) and whole body calcium concentrations increased by increasing the dietary vitamin K supplementation levels. Intestinal MK-4 concentration was similar in all dietary treatments. Analysis of total plasma prothrombin concentration by broken-line regression indicated that the optimum dietary niacin requirement of juvenile grouper is about 15 mg/kg diet.