Dietary Iron Requirements of Adult GIFT Tilapia (Oreochromis niloticus)

Abstract

Dietary iron requirement of adult Nile tilapia (Oreochromis niloticus), genetically improved farmed tilapia (GIFT strain), was determined in this study through a 77 day feeding trial. Diets with six concentrations of iron (45.55 - the control group, 94.91, 193.62, 292.34, 391.05, and 489.77 mg iron/kg diet) from ferrous sulfate were formulated and hand-fed to adult GIFT (initial body weight 174.58±3.49g). The results indicated that no fish died in all groups. Weight gain ratio, feed efficiency rate, as well as specific growth rate decreased in relation to increasing dietary iron levels, and reached the lowest when supplemented with 489.77 mg iron/kg diet. Crude body fat content showed an increasing trend in relation to increasing dietary iron levels. The iron content in the body, vertebrae, and liver significantly increased with dietary iron levels which reached up to 391.05 mg iron/kg diet. The number of red blood cells, the hemoglobin content and the packed cell volume was highest in 94.91 mg iron/kg group. In conclusion, dietary iron made no obvious improvement on growth performance, but improved hematopoietic function of adult Nile tilapia, reared in freshwater. We found that no additional iron needs to be added to the adult Nile tilapia (174.6–558.1 g) feed based on the growth, whereas broken-line regression analysis were used to determine the optimum iron requirements for maximum hemoglobin levels, the dietary iron requirement for hemoglobin was 120.94 mg iron/kg diet with ferrous sulfate as a source of iron.