EFFECTS OF THE DELETION OF MG OR FE FROM SEMI PURIFIED DIETS ON GROWTH AND EFFICIENCY OF FEED-UTILIZATION OF YELLOW CROAKER NIBEA-ALBIFLORA

Yellow croaker Nibea albiflora, (mean initial weight 28.7 g) were fed on casein based semi purified diets with (control) or without suppleme nt of either magnesium (No-Mg) or iron (No-Fe) over a 14 weeks period at 22-23.5 degrees C. At the end of feeding trial growth performance, hematological characteristics and chemical analysis of the body compos ition were examined. Growth, feed efficiency and hepatosomatic index i n fish fed Fe deficient diet differed significantly from those of cont rol fish. Moreover, hemoglobin content, hematocrit value and plasma Fe content of the fish fed on diet without Fe supplement exhibited signi ficantly lower values, while higher values of plasma triglyceride, tot al cholesterol and unsaturated iron binding capacity (UIBC) were detec ted compared to the control group. No difference, however, was noted i n the hematological characteristics between the Mg deficient diet and the control. In fish fed Fe deficient diet, slight reduction in bone l ipid and in the ash contents of Mn and Cu was observed, through Fe lev el remained similar to the control. The results obtained from the pres ent study show that Mg requirement can be met from either or both diet or surrounding water, whereas, dietary Fe is essential to prevent ane mia in yellow croaker.