Comparison of the nasopharyngeal bacterial microbiota of beef calves raised without the use of antimicrobials between healthy calves and those diagnosed with bovine respiratory disease

Abstract

 It has been shown that the composition of the nasopharyngeal bacterial microbiota plays a role in respiratory health. However, the role of this microbiota in the development of bovine respiratory disease (BRD) is still not well defined. What we know about the composition of the bovine nasopharyngeal bacterial microbiota mainly comes from beef calves that have received mass medication (metaphylaxis) with an antimicrobial on arrival at a feedlot. Unfortunately, antimicrobials do not just target pathogenic bacteria, and antimicrobial use can have an impact on the entire respiratory microbiota, including commensals. There are currently no data on the composition of the nasopharyngeal microbiota of healthy feedlot cattle and those diagnosed with BRD that are raised without antimicrobials (i.e. natural cattle), limiting our understanding of the disease. As the beef industry begins to move away from the use of antimicrobials, this information will become increasingly valuable. Therefore, the objective of this study was to characterize and compare the nasopharyngeal bacterial microbiota in feedlot cattle raised without antimicrobials that were healthy or diagnosed with BRD.