Influence of Dietary Phytic Acid on Growth, Feed Intake, and Nutrient Utilization in Juvenile Japanese Flounder, Paralichthys olivaceus

A feeding trial was conducted to determine the effect of phytic acid (IP6) on growth, feed intake, nutrient digestibility, body composition, nutrient retention, and plasma mineral contents in juvenile Japanese flounder, Paralichthys olivaceus. Five test diets containing different levels of IP6 (0, 5.1, 10.4, 13.5, and 20.6 g IP6/kg diet) were fed to juveniles (average body weight = 4.58 g). After a 50-d feeding trial, there were no negative effects on growth and feed intake in fish fed diets supplemented with IP6 up to 10.4 g IP6/kg. However, weight gain and feed intake of fish fed diets containing 13.5 and 20.6 g IP6 were significantly lower than those of control group. Total phosphorus (P) contents of fish were not significantly different among fish groups fed the diets containing up to 10.4 g IP6. Plasma inorganic P and magnesium (Mg) contents significantly lowered with increased dietary IP6. Dietary IP6 significantly reduced zinc level in the fish vertebra. The significantly lower contents of vertebral Ca and Mg were found in fish fed diets containing the highest level of IP6 (20.6 g/kg). This study demonstrated that dietary IP6 with more than 13 mg/kg negatively affected the growth performances, body composition, and nutrient utilization in juvenile Japanese flounder.