The nasopharyngeal microbiota of feedlot cattle

Abstract

The bovine nasopharyngeal tract plays an important role in animal health and welfare by acting as a site for the carriage of pathogens causing bovine respiratory disease, a condition which results in significant morbidity and mortality in feedlot cattle. We characterized the bacterial nasopharyngeal microbiota in cattle at feedlot entry (day 0) and day 60 using 454 pyrosequencing. We also identified the most frequently isolated aerobic bacteria from nasopharyngeal swabs after plating onto three types of media. The cattle nasopharyngeal microbiota was composed primarily of Proteobacteria (68.9%) and Firmicutes (19.2%). At the genus-level, there was more inter-individual variability and a total of 55 genera were identified. The genera Pseudomonas (23.7%), Shewanella (23.5%), Acinetobacter (17.5%), and Carnobacterium (12.2%) were most prevalent at entry, while after 60 days in the feedlot, Staphylococcus (20.8%), Mycoplasma (14.9%), Mannheimia (10.4%), and Moraxella (9.4%) were dominant. The nasopharyngeal microbiota also became more homogenous after 60 days in the feedlot and differed in structure at day 0 and 60. Using culture-based methods, the most frequently isolated bacteria from nasopharyngeal swabs were Bacillus, Staphylococcus, Moraxella, Pasteurella, and Mannheimia. These results provide insight into the nasopharyngeal microbiota of cattle and demonstrate that specific changes take place during feedlot production.

Figure 1

Classification of 16S rRNA gene sequences at the (A) phylum and (B) genera level for each individual day 0 and day 60 nasopharyngeal sample. Numbers on the x-axis indicate animal identification number. All phyla are shown in (A) and in (B) only those genera comprising greater than 1% of the sequences at either entry or exit are displayed.

Figure 2

Principal coordinate analysis (PCoA) of the (A) unweighted UniFrac distances and (B) weighted UniFrac distances for day 0 and day 60 nasopharyngeal samples. The percent variation explained by each principal coordinate is indicated on the axes.