Evolution of the nasopharyngeal bacterial microbiota from spring processing to 40 days after arrival at the feedlot in beef calves

Abstract

The stability of the bovine nasopharyngeal bacterial microbiota has been shown to play a crucial role in respiratory health. The combination of microbiota-based inhibitory effects and the protective effects of the host’s immune system creates a stable environment in the nasopharynx. However, a loss of stability in the microbiota may decrease the host’s ability to contain opportunistically pathogenic bacteria and increase the risk of foreign pathogens colonizing the upper respiratory tract. These pathogens can proliferate and progress into the lower respiratory tract, potentially leading to pneumonia. Different factors, including antimicrobial usage, commingling, stress, and concurrent viral infection can have an impact on the stability of nasopharyngeal microbiota. In humans, it has been shown that the respiratory bacterial microbiota evolves toward an adult-like profile within the first months of life. Certain bacterial profiles, once established, can remain stable over time, demonstrating a resiliency against respiratory infection. Previous longitudinal studies looking at the evolution of the nasopharyngeal bacterial microbiota in beef cattle have only centered around significantly stressful events, such as weaning and arrival at a feedlot, limiting our understanding of how respiratory microbiota evolve from an early age. Therefore, the objective of this study was to characterize the nasopharyngeal bacterial microbiota and its evolution from spring processing to 40 days after arrival at the feedlot.