Effect of metaphylaxis on the temporal dynamics of Mannheimia haemolytica, Mycoplasma bovis, Histophilus somni and Pasteurella multocida in the upper respiratory tract of low-risk cattle

Bovine respiratory disease (BRD) is the main cause of morbidity and mortality in beef cattle. Four bacterial species (Mannheimia haemolytica, Histophilus somni, Pasteurella multocida and Myco­plasma bovis) are considered key pathogens in the development of BRD. To minimize the risk of developing BRD, beef cattle are often administered antibiotics at the time of their arrival to a feedlot (also known as metaphylaxis). While metaphylaxis is a widely employed control strategy, little knowledge exists regarding its impact on the microbiome of cattle at low risk for developing BRD. This study aimed to identify the influence of different metaphylactic treatments on the temporal dynamics of BRD-associated bacterial pathogens in the upper respiratory tract of cattle at low risk for BRD development.