The nasopharyngeal microbiota of beef cattle before and after transport to a feedlot
Citation
Holman, D.B., Timsit, E., Amat, S., Abbott, D.W., Buret, A.G., Alexander, T.W. (2017). The nasopharyngeal microbiota of beef cattle before and after transport to a feedlot. BMC Microbiology, [online] 17(1), http://dx.doi.org/10.1186/s12866-017-0978-6
Plain language summary
In North America, beef cattle are typically transported to a feedlot where they are finished on a high-grain diet until slaughter. Bovine respiratory disease (BRD), also called shipping fever, remains the most common cause of morbidity and mortality after feedlot placement, resulting in significant economic losses. Cattle are most susceptible to BRD after feedlot placement. Recently, it has been recognized that the microbiota (all microorganisms) are critical to respiratory health and that commensal bacteria have a role in inhibiting bacterial pathogens. However, limited information exists on how the bovine respiratory microbiota changes throughout production, and what role any disturbances in the microbiota may have on pathogen growth. Therefore, we used high-throughput DNA sequencing to characterize the upper respiratory tract microbiota of beef cattle heifers that were transported to a feedlot from a closed herd. Within two days of transport to the feedlot, the microbiota changed significantly, increasing in diversity. In addition, a variety of bacteria increased in abundance, including some known respiratory pathogens. These results demonstrated that there is an abrupt shift in the upper respiratory tract microbiota of cattle after transportation to a feedlot. This may have importance for understanding why cattle are most susceptible to BRD after feedlot placement. Future studies are needed to evaluate whether the bovine respiratory microbiota can be manipulated to enhance protection against BRD at feedlot entry.
Abstract
Background: The nasopharyngeal (NP) microbiota plays an important role in bovine health, comprising a rich and diverse microbial community. The nasopharynx is also the niche for potentially pathogenic agents which are associated with bovine respiratory disease (BRD), a serious and costly illness in feedlot cattle. We used 14 beef heifers from a closed and disease-free herd to assess the dynamics of the NP microbiota of cattle that are transported to a feedlot. Cattle were sampled prior to transport to the feedlot (day 0) and at days 2, 7, and 14. Results: The structure of the NP microbiota changed significantly over the course of the study, with the largest shift occurring between day 0 (prior to transport) and day 2 (P < 0.001). Phylogenetic diversity and richness increased following feedlot placement (day 2; P < 0.05). The genera Pasteurella, Bacillus, and Proteus were enriched at day 0, Streptococcus and Acinetobacter at day 2, Bifidobacterium at day 7, and Mycoplasma at day 14. The functional potential of the NP microbiota was assessed using PICRUSt, revealing that replication and repair, as well as translation pathways, were more relatively abundant in day 14 samples. These differences were driven mostly by Mycoplasma. Although eight cattle were culture-positive for the BRD-associated bacterium Pasteurella multocida at one or more sampling times, none were culture-positive for Mannheimia haemolytica or Histophilus somni. Conclusions: This study investigated the effect that feedlot placement has on the NP microbiota of beef cattle over a 14-d period. Within two days of transport to the feedlot, the NP microbiota changed significantly, increasing in both phylogenetic diversity and richness. These results demonstrate that there is an abrupt shift in the NP microbiota of cattle after transportation to a feedlot. This may have importance for understanding why cattle are most susceptible to BRD after feedlot placement.