Each experimental diet was fed to triplicate groups of 25 juveniles each with initial average weights of 2.40 ± 0.01 g in the circular tank for 90 days. Weight gain, protein efficiency ratio, plasma complement 3, plasma complement 4, white blood cell, red blood cell and hemoglobin content significantly increased with increasing dietary VA level, reached a peak with 1934 or 3885 IU kg− 1 VA, and then decreased.