Study examines livestock trailer cleanliness using bioluminescence

Trial evaluated the back door flush gate, rear drivers side access door, the belly flush gate, belly side access door, and nose side access door.

November 27, 2023

4 Min Read
National Pork Board

Livestock trailer cleanliness is normally determined by visual evaluation, assessing if it is free of organic material and suitable to return to a farm. However, studies have shown visual inspection may be insufficient to ensure cleanliness and reduce disease transmission risk because viruses and bacteria are microscopic.

In a Swine Health Information Center Wean to Harvest Biosecurity Program study conducted by Dustin Boler, Carthage Innovative Swine Solutions, and Bailey Harsh, University of Illinois, the suitability of bioluminescence for evaluating trailer cleanliness was assessed and confirmed as a prospective testing method.

SHIC’s Wean-to-Harvest Biosecurity Research Program, funded with the Foundation for Food & Agriculture Research and the Pork Checkoff, addresses biosecurity gaps, like trailer cleanliness, in the pork industry. Boler and Harsh’s research evaluated the performance of two adenosine triphosphate instruments to estimate cleanliness in livestock trailers.

Results of the ATP instruments were compared to aerobic plate counts (bacterial contamination) to determine if ATP bioluminescence could be used as an indicator of trailer cleanliness as an objective substitute for visual inspection that usually occurs after the cost to dry a truck with propane has been incurred.

ATP is a source of cellular energy present among all living organisms. This includes viruses and bacteria remaining after a commercial trailer cleaning. ATP bioluminescence uses a chemical reaction where a swab is used to detect the presence of ATP. The more ATP that is present, the greater the chemical reaction.

This technology uses the same chemical process a firefly uses to illuminate. When ATP is exposed to the enzyme, a light is produced – the more ATP present, the brighter the light. The intensity (brightness) is measured in relative light units. A greater RLU indicates more ATP and reduction in overall cleanliness. In this case, the brighter the swab glows, the more ATP is present, the more potential microbial contamination is present.

The goals of this project were to determine the areas of the trailer with the greatest surface contamination, the correlation between microbial counts and RLUs, and the number of locations that need to accurately determine surface cleanliness.

Livestock trailers at two commercial trailer washes were evaluated in this study. One of those locations included trailers known to transport livestock from a porcine reproductive and respiratory syndrome virus or porcine epidemic diarrhea virus positive site. In total, 100 livestock trailers were tested using bioluminometers to determine the amount of ATP remaining after a commercial trailer wash.

Protocols are in place to prevent people from entering a livestock trailer after it has been cleaned to prevent contamination. For this technology to be adopted into practice, locations inside the trailer that are accessible from outside the trailer must be evaluated. This trial evaluated the back door flush gate, rear drivers side access door, the belly flush gate, belly side access door, and nose side access door.

Study results indicated the areas of highest concern sampled in this study were the nose access door and the back door flush gate as detected both by ATP bioluminescence and aerobic plate counts. A key finding of this research was that nose access door of trailers having one was the area least likely to be adequately cleaned, but only a few trailers actually had nose access doors. Nearly all of the trailers evaluated had a back door flush gate, making it a logical place to swab a livestock trailer to determine the overall cleanliness.

The ability of ATP to be used as an indicator of trailer cleanliness was associated with the instrument used, with the 3M machine being most closely correlated with bacterial contamination. Swabs were also collected to determine the presence of PEDv, but all swabs were PCR negative. These data suggest that ATP bioluminometers can be used in livestock trailers to quickly and objectively determine the general cleanliness of the trailer instead of a visual inspection. Bacterial swabs to determine aerobic plate count levels can also be used to determine the effectiveness of the cleaning protocol.

SHIC, FFAR and Pork Checkoff launched the two-year Wean-to-Harvest Biosecurity Program in the fall of 2022. The first call for research proposals was announced in October 2022 with the goal of investigating cost-effective, innovative technologies, protocols or ideas to enhance biosecurity during the wean-to-harvest phases of swine production. Round one projects, launched in March 2023, received approximately $1 million. Round two proposals were due April 2023 and began summer 2023. Approximately $2.3 million is available for the entire program.

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