Toward a better understanding of upper respiratory tract bacterial colonization in neonatal beef calves

Bovine respiratory disease (BRD) is one of the most costly dis­ease complexes to the beef industry. Bacterial pathogens asso­ciated with BRD include Mannheimia haemolytica (MH), Histoph­ilus somni (HS), Mycoplasma bovis (MB) and Pasteurella multocida (PM). However, the source and timing of when these bacterial pathogens colonize in the upper respiratory tract of neonates is poorly understood. The objective of this study was to evaluate the bacteria and viruses present in the upper respiratory tract of neonatal beef calves immediately following parturition and for the first 24 hours of life.