Maternal antibody transfer efficiency: The impact of M. bovis-BoHV-1 combined vaccine.

Bovine respiratory disease (BRD) is a complex and one of the most costly diseases caused by multiple bacterial and viral infections. Cattle of almost all ages are susceptible to BRD, with young day-old newborn calves being the most at risk. The ability of newborn calves to acquire passive immunity from milk, appears to be a critical issue in immunological evaluation. This study evaluated the maternal antibody transfer capacity of an attenuated and marker M. bovis-BoHV-1 combined vaccine. Results demonstrated that the combined vaccine had a good maternal antibody transfer ability, as evidenced by the detection of high titers of specific antibodies against M. bovis and BoHV-1 in milk of heifers and serum of colostrum-fed newborn calves, with M. bovis antibodies persisting up to 28 days postpartum, peaking at 77.8 % on day 7. Besides, total IgG levels in milk and calf serum were also markedly elevated and consistently different from controls during the first two weeks after birth (p < 0.05). In conclusion, the combined vaccine exhibited favorable maternal antibody transfer ability, and the protection generated by this passive immune response on calves can last for a prolonged period of time, which is essential for improving calf survival.