A field comparison of heterologous and homologous routes of administration of modified live vaccines for the control of bovine respiratory disease in recently weaned beef calves.

The use of metaphylactic antimicrobials to control bovine respiratory disease (BRD) is under increased scrutiny; therefore, effective immunization is becoming a priority. Stimulation of an effective immune response is challenging because calves are often primed with injectable (IJ) vaccines, in the face of maternal antibodies which can interfere with the immune response. Maternal antibody interference may be bypassed with use of intranasal (IN) vaccines. This study represents one of few independent vaccine field trials and it demonstrated no significant differences in post-weaning BRD morbidity/mortality or average daily gain in beef calves primed with either an IN or IJ vaccine. Copyright and/or publishing rights held by the Canadian Veterinary Medical Association.