Introduction. Bovine respiratory disease (BRD) is the most costly disease of beef cattle in North America (1). It is also one of the most extensively studied, with research beginning in the late 1800s and continuing today.A recent review examined various proposed predisposing factors (2).iagnosis of bovine respiratory disease. Perhaps the greatest hindrance to better elucidating factors associated with BRD is difficulty in defining and/or identifying the disease. Postmortem diagnosis, in the absence of prior treatment, is the most definitive means.