Serum samples were collected before vaccination as day 0 and additional blood samples were obtained on days 28, 60, 90, and 120 postvaccination and analyzed via virus neutralization test. immunity for incessant protection. Keywords: calf, foot-and-mouth disease, high potency vaccine, maternal antibody, virus neutralization Introduction Foot-and-mouth disease (FMD) is one of the most important viral diseases of cloven-hoofed Lomerizine dihydrochloride animals. The causative agent is in the genus, a member of the picornavirus family. Mortality from FMD is usually high in young animals due to the affinity of the virus for myocardial tissue [24]. In addition, great economic losses occur due to trade restrictions in and with countries where the disease is present. Mass vaccination is an effective method to control FMD and is frequently utilized in Lomerizine dihydrochloride endemic regions [15]. Sufficient protection of young animals is an important issue in mass vaccination campaigns [19] given that susceptible young animals can aggravate outbreaks [9]. In cattle, passive transfer of antibodies from dam Lomerizine dihydrochloride to neonate is possible via colostrum, which is crucial for protection against many calf diseases. The dam’s age affects the amount Grem1 and quality of colostrum and thereby the antibody titer circulating in calf serum [7]. An inadequate immune response in young animals in many livestock species (pigs, cattle, and horses) has been reported [20]. Some immune response-related problems are associated with the vaccination of neonates, including the neonate’s immature immune system and the presence of maternal antibodies transferred from the dam [3,20]. Moreover, frequent vaccinations may lead to tolerance to antigens, and a high level of cortisones can negatively affect immunization responses in neonatal calves [3]. The presence of maternal antibodies decreases or may completely disappear after immunization of neonates. This outcome is usually observed with all types of vaccines, and there are numerous reports [1,8,10,23] demonstrating that the presence of maternal antibodies affects immunization responses negatively. In theory, a vaccine should be administered after maternal antibodies have completely disappeared [20]. Many factors are involved in the duration of the presence of maternal antibodies in neonates. It is difficult to predict when maternal antibody disappearance is usually complete; therefore, measurement of antibody level in a neonate is necessary. However, in practice, it is difficult to measure the antibody level of each individual. Hence, a prime-boost vaccination strategy is used to overcome maternal antibody interference [5,20,22,24]. An oil adjuvant vaccine can overcome maternal interference via a single immunization [21]. The same study suggested that vaccines with an aluminum hydroxide adjuvant cannot overcome maternal immunity [21]. According to European Pharmacopeia [4], the minimum protective level of an FMD vaccine cannot be less than 3 PD50. In addition, vaccines with a 6 PD50 protective level can be used in emergency situations. When a double emulsion vaccine Lomerizine dihydrochloride of 3 PD50 potency is used in a vaccination campaign, 71% of the vaccinated livestock population are guarded, whereas vaccination with the same vaccine but with a 6 PD50 potency confers 81% protection [14]. In a vaccine efficacy study, a single dose of immunization can only prevent 69% of clinical FMD and 83% of severe symptoms [15]. Vaccination campaigns with > 3 PD50 oil adjuvant vaccines have been used in Turkey to combat FMD, but recently, that strategy was replaced with one that uses a 6 PD50 vaccine. The minimum age of animals to be vaccinated during a vaccination campaign, the potency of the vaccine, and the booster dose necessary to overcome maternal antibody interference have yet to be determined. The aim of this study was to investigate the antibody response of calves with various levels of maternal antibodies to single and booster immunizations with FMD vaccines of different potencies. Materials and Methods Vaccine Two different batches of commercial Turvac-oil FMD trivalent vaccine of 3 PD50 and 6 PD50 Lomerizine dihydrochloride potencies for type A virus, produced by the SAP Institute, Turkey, were used in this study. Montanide ISA 206, (Seppic, France) oil adjuvant was used to prepare double emulsions (water-in-oil-in-water). The O TUR 07, ATUR 04/06 (A IRAN 2005), and ASIA-1TUR 11 inactivated virus cultures were.