Source: BCRC
Project Title
Determining the Effect of Stress on the Respiratory Microbiome of Cattle During Transportation
Researchers
Trevor Alexander (Agriculture and Agri-Food Canada Lethbridge)
Graham Plastow (University of Alberta); Karen Schwartzkopf-Genswein, Tim McAllister, Dallas Thomas (Agriculture and Agri-Food Canada Lethbridge)
BACKGROUND
Transportation is stressful, but so is loading and unloading. Research hasn’t determined whether requiring mandatory rest stops to break up long distance transport into more, shorter trips will reduce or increase stress. We do know that stress can increase the risk of diseases like BRD, possibly by disturbing the microbes that naturally live in the respiratory tract and allowing disease-causing microbes to establish a foothold. This project examined how transportation rest stops affect the respiratory microbiome using cattle involved in an ongoing Beef Cluster funded project.
OBJECTIVES
Analyze the respiratory microbiome (bacterial commensals and pathogens; viral agents) in comparison to stress markers (cortisol, blood cell counts, haptoglobin) in cattle subjected to the following transportation stress models:
- varying rest stop durations (including no rest stop)
- varying sources of transported calves (ranch-direct versus auction market-derived)
- varying transportation times
WHAT THEY DID
Nasopharyngeal swabs were collected from calves from various sources (single-source ranch vs. auction mart calves) that had been transported and rested for various times. Swabs were collected at different time points in relation to loading, unloading, rest stops, and after feedlot placement, and were examined to see if there were differences in the microbial populations of the upper respiratory tract over time. They looked to see whether these changes in respiratory microorganism population structure were related to physiological indicators of stress, animal health and performance during the first 30 days in the feedlot.
WHAT THEY LEARNED
The microbial populations in the bovine respiratory tract underwent significant and relatively rapid changes in structure and composition when cattle were transported and placed in a feedlot. Microbial diversity generally increased after feedlot arrival, likely due to the feedlot being a source of novel bacteria entering the respiratory tract. These changes continued as the animals adapted to the feedlot, in both commensal and pathogenic bacteria. However, several key microbial types gradually became dominant and established a more stable population over time.
Cortisol is indicator of acute stress and haptoglobin can highlight stress and inflammation. While correlations between cortisol and haptoglobin were observed for several of the most abundant genera, there were no clear trends showing a relationship between these stress markers and bacteria.
Notably, when cattle were provided a rest stop during transportation, several key bacterial genera associated with BRD (Mannheimia, Histophilus, Pasteurella) were higher for most sampling times after feedlot placement compared to animals that were not given a rest stop. This finding was observed in several studies. Similarly, more sampling time points had elevated levels of BRD-associated genera when auction market cattle were compared to ranch-direct, and cattle with longer transportation times were compared to those with shorter transportation times.
WHAT IT MEANS
This research indicated that rest stops during transportation, auction market placement, and longer transportation times may be risk factors for BRD, based on increased abundance of BRD-associated genera in the upper respiratory tract after cattle were placed in feedlots. Because BRD incidence was low in the studies performed, it was not possible to correlate the abundance of BRD-associated genera to animal health. Larger-scale studies are needed to confirm how these transportation variables impact BRD incidence.
