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Previous research has demonstrated that pathogen loads carried on the hides of cattle increase
from the time they leave a feedlot to the time they arrive at a harvest facility. The cause of this
increase is not fully understood. Initially, it was hypothesized that cross-contamination was
occurring while cattle were on trucks and that the increase in pathogens might be due to the
cleanliness of the trucks. A 2004 research project indicated that the cleanliness of the truck did
not necessarily impact pathogen loads on hides during transport. During the course of this
research, the investigators observed that a cloud of dust was generated at every load-out. It was
hypothesized that this air-borne particulate matter that is essentially pulverized fecal material
may be at least partially responsible for the increase in pathogen prevalence. A subsequent
research project supported that assumption. Exposure to the air-borne particulate matter
generated from the surface of loading pens significantly increased the prevalence and quantity of
E. coli O157 and Salmonella recovered from cattle hides. <P>
Feedlot load-out areas may be a critical control point in reducing pathogen loads on beef
carcasses. Control measures should be investigated to prevent increases in pathogen loads and
ultimately to reduce pathogen loads on carcasses and in ground beef. <P>
This research project was designed to determine if preventing dust generation would result in a
decrease in Salmonella pathogen numbers by comparing results from a clean concrete load-out
area in a feedlot versus a dirt loading area with no dust control measures.
Findings:
The researchers found no changes in the total population or total number of animals that tested
positive for Salmonella before or after loading or between the clean and dirty load-out areas. On
average, 80 percent of the animals at all sampling locations tested positive for Salmonella. <P>
Samples collected from the pen floors in both the clean and dirty load-out areas were 100 percent
positive for Salmonella. Very little of the Salmonella appeared to be transferred to the air. In the
clean load-out area, no Salmonella was detected in the air samples, while in the dirty area 15
percent of the air samples tested positive for Salmonella. <P>
The high initial Salmonella incidence on the hides of the cattle meant that the small amounts that
appeared to be transferred to the air did not have significant impacts on the pathogen status of the
animals. <P> For complete projects details, view the <a href="http://www.beefresearch.org/CMDocs/BeefResearch/2008_Miller_Salmonella%…; target="_blank">Project Summary. </a>