First Defense® delivers Immediate Immunity™ for newborn dairy and beef calves. First Defense® is the only USDA and CFIA approved, colostrum derived, product to defend against K99+ E. coli and coronavirus. First Defense® is the easiest scours prevention product to use with the most accurate dosage. OMRI listed, suggested for use in organic operations. Dosage and Administration: Administer one bolus per calf within the first 12 hours after birth. Do not vaccinate calves with oral coronavirus or rotavirus products within 5 days of administering First Defense®.