What is the core and risk-based vaccination schedule recommended for beef cattle?

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Accepted Answer

Bovine respiratory disease (BRD) is the primary vaccination target in beef cattle, and the timing of vaccination relative to stress and disease challenge is the central determinant of program efficacy. The sources do not provide a single enumerated core/risk-based schedule with specific antigen-by-antigen dose intervals, so what follows reflects the evidence directly available. BRD remains the most prevalent and costly infectious disease in North American beef cattle, with the greatest impact in stocker and feedlot sectors. Its etiology involves stress-induced immune dysfunction, viral infection, and bacterial bronchopneumonia acting together, making vaccination against both viral and bacterial BRD pathogens a standard component of cow-calf, stocker, and feedlot health programs.1 Economic losses from BRD occur most commonly in beef calves at weaning (5–8 months of age), preweaning beef calves younger than 5 months, and dairy calves younger than 3 months.7 Vaccination timing is critical — vaccination is not equivalent to immunization. Immunization requires adequate time for a competent host immune system to mount a response to vaccine antigen; administering vaccine to a stressed, immunosuppressed animal at feedlot arrival does not guarantee that response.6 Despite this, nearly all consulting veterinarians recommend vaccination of high-risk calves on feedlot arrival — a practice that fails to account for stress-induced immunosuppression and other host factors that reduce vaccine efficiency.13 Endotoxin stacking from simultaneous administration of multiple bacterins is a recognized concern in high-risk cattle. The additive endotoxin load from multiple bacterin products given concurrently may have adverse effects, though the sources identify this as an area requiring further evidence-based evaluation before specific revised protocols can be issued.13 Modified-live virus (MLV) and killed virus (KV) vaccines are both commercially available for BRD viral pathogens, with di