S. iniae was cultured as described for injection and immersion administration. After 24 hrs, cells were checked for sterilization, harvested and washed three times with 0.85% NaCl. The harvested cells were dehydrated using FreeZone® 6 liter console freeze-dry system with shell freezer (Labconco corporation, Missouri). The dehydrated cells were incorporated in feed for oral administration. Two isonitrogenous test diets were formulated to contained 30% protein, 7% fat, and 5% fiber. All diets have the same composition except the level of vaccine added to achieve 0 and 1% for control and experimental diet, respectively. The composition of the test diets is shown in Table 1