Vaccination strategies for beef cattle
Vaccines are used at various times during the beef production system with the goal of safe immunization and prevention of diseases caused by viral and bacterial pathogens. Immunization involves a complicated but coordinated network of innate and adaptive immune responses to antigen(s) over a period of days to weeks, ideally in an immunocompetent host in a state of homeostasis. However, bovine respiratory disease (BRD) involves stress and immune dysfunction in its pathogenesis, it usually occurs soon after arrival, and vaccination with modified-live virus (MLV) during stress and natural BRD challenge may be harmful in some animals. Complicated factors to consider regarding vaccination of beef cattle include timing, antigen inclusion, route of administration, and frequency of vaccination. Calves that are marketed to feedlots without previous vaccination are typically considered high-risk because they are likely to also lack weaning, deworming, and castration prior to marketing. Furthermore, high-risk cattle experience stress-induced immune dysfunction because multiple stressors occur simultaneously. Veterinary practitioners should consider new research on vaccination during physiological stress and natural pathogen exposure to better guide recommendations and expectations of their clients.