However, one single seronegative cow was culled before parturition and was excluded from the study, and five seropositve cows that aborted during the study (from Days 133 to 220 of gestation) were also excluded from the study because the number of aborting cows was insufficient to provide significant results. The final data analyzed were obtained from 46 cows (11 primiparous and 35 pluriparous in their second to sixth lactation period) with a mean calving to conception interval of 105 d (range, 58 to 203 d).