The Effects of Dietary Magnesium (Mg) Supplementation on Growth Performance of Adult Japanese Seabass (Lateolabrax japonicas)

Abstract

Japanese seabass, Lateolabrax japonicus (mean initial weight 204.5 g) were fed one of six casein-dextrin-based diets containing graded levels of magnesium (Mg) (184, 278, 487, 929, 1299, and 1737 mg/kg) for 10 weeks with the water-borne Mg concentration of 985 mg/L. Magnesium sulphate was used as the Mg source in the diets. The experiment was carried out in floating sea cages. Growth, survival rate, superoxide dismutase (SOD) activities, glutathione peroxidase (GPx), malondiadehyde (MDA) contents and tissue mineral contents were measured to investigate the effect of dietary magnesium in seabass. After 10 weeks, dietary magnesium supplementation did not improve the growth performance or feed efficiency of adult seabass. On the contrary, negative effects on growth performance, decreased glutathione peroxidase (GPx) and increased malondiadehyde (MDA) contents were observed in seabass fed Mg diets with 929, 1299 mg/kg and 1737 mg/kg, and feed efficiency (FE) exhibited a decreasing tendency with increasing Mg supplemental levels, which indicates the Mg requirement of seabass was met in fish fed the basal diet. Survival, hepatosomatic index, viscerosomatic index, condition factor, and Mg and Ca concentration in whole-body, vertebrae, and scales were not affected by dietary Mg supplementation (P<0.05).