Neutralizing antibody responses in preconditioned calves following vaccination for respiratory viruses.

Calf preconditioning programs that include vaccinations against common respiratory pathogens are beneficial; however, optimal vaccination protocols have not been determined. In the study described here, calves were placed in a preconditioning program and assigned to one of nine vaccine regimens, each consisting of some combinations of killed or modified-live virus vaccines against bovine herpesvirus-1 (BHV-1), bovine viral diarrhea virus (BVDV), parainfluenza-3 (PI-3) virus, and bovine respiratory syncytial virus (BRSV). Serum virus-neutralization antibody titers were measured at four time points. At the end of the study, all vaccinated calves had higher antibody titers to BVDV, BHV-1, and PI-3 but not BRSV. Calves on a vaccine program that included at least one dose of modified-live virus vaccine had higher virus-neutralizing antibody titers against BVDV than did calves receiving only killed vaccines. Calves on a program with a combination of modified-live and killed virus vaccines had higher virus-neutralizing antibody titers to BHV-1 than did calves receiving only killed or only modified-live virus vaccine. Preconditioning programs that include vaccinations should incorporate modified-live vaccines to maximize virus-neutralizing antibodies in serum.