We investigated the dynamics and duration of antibody titer against Pasteurella multocida in Japanese Black calves. Twenty unvaccinated calves from two Japanese Black breeding farms in Japan, were studied. Blood samples were obtained from all calves at 1, 4, 8, 12, 16 and 20 weeks after birth, and also obtained from their dams once at 1 week after calving. Antibody titer against P. multocida in calves at 1 week of age after birth was well correlated with that in their damsat 1 week after calving. Maternally derived antibody titer against P. multocida reached the lowest at 4 weeks of age. Calves began producing antibody against P. multocida by themselves between 4 and 8 weeks of age. These results might help designing a vaccination program against P. multocida for Japanese Black calves.

Key words: Antibody titer, Immunity, Japanese black calves, Pasteurella multocida