Preparing for the Next Animal Disease Outbreak – Feed Mill Hygiene and Decontamination

Written by: Guest   |   March 25, 2024

pathogen control, ag & food research, Biosecurity, feed & food safety, African swine fever, formaldehyde

By: Olivia Harrison; Chad Paulk, Ph.D.; Jordan Gebhardt, D.V.M. and Ph.D.; Jason Woodworth, Ph.D.; and Cassandra Jones, Ph.D. 

Since the outbreak of the porcine epidemic diarrhea virus (PEDV) in 2013, the feed and livestock industries have worked to gain a better understanding of pathogen transmission through feed and the supply chain. Multiple studies have documented the distribution of viral pathogens in mills after contamination, the stability of viruses in feed and ingredient matrices, and virus reduction using chemical mitigants or extended holding times.  

However, little research has focused on how best to decontaminate a feed mill following the initial pathogen exposure. This is problematic, given the feed industry will be relied upon to get back online as quickly as possible following an animal disease outbreak to service U.S. farms.  

With African swine fever virus (ASFV) so close to the continental United States, helping the feed industry develop hygiene and decontamination strategies to implement quickly and efficiently following an animal disease outbreak at a facility is all the more urgent. Therefore, last year, several researchers at Kansas State University, with support from American Feed Industry Association members and the Institute for Feed Education and Research (IFEEDER), sought to answer this question and hopefully provide more information to support feed mills developing their plans.  

The Experiment 

To better understand feed mill hygiene and decontamination, the K-State Feed Safety team, along with several collaborating universities and industry partners, designed a series of experiments to provide potential strategies for feed mills in the event of pathogen contamination. These experiments utilized feed that was purposefully inoculated with viruses already present in the United States, including PEDV, porcine reproductive and respiratory syndrome virus (PRRSV), and Seneca Valley Virus 1 (SVV1; aka Senecavirus A). Since SVV1 is commonly used as a surrogate virus for foot and mouth disease and is found to be more stable than ASFV, the research team only reported the SVV1 results here as a model for exposure to a foreign animal disease.  

The experiments, conducted at KSU’s Cargill Feed Safety Research Center, investigated the following strategies:  

Experiment 1: Flushing feed mill equipment with high levels of chemical mitigants (formaldehyde-based mitigants) to reduce pathogen presence in subsequent batches of feed and in the environment. 

• Experiment 2: Pelleting (conditioned feed at 180°F for 30 seconds) as a point-in-time mitigant for pathogen control. 

• Experiment 3: The use of either chemical (chlorine dioxide gaseous fumigation) or heat (portable electric heaters) to reduce pathogen presence on the feed manufacturing equipment and in the environment.  The researchers collected feed, environmental and/or dust samples during the hygiene and decontamination process, analyzing them via polymerase chain reaction (PCR) tests to detect if any genetic virus material was present. The selected samples were then used in a swine bioassay to determine infectivity.  

The Results 

Overall, the results showed that there are ways feed mills can reduce the viral load on their equipment and in the mill environment, but none of the strategies tested completely removed the virus. However, the chances of pigs becoming sick following decontamination is greatly reduced, the study showed. 

Experiment 1: Flushing with high levels of chemical mitigants 

• This method of flushing the equipment with either liquid formaldehyde (at a 1.5% inclusion rate) or undiluted dry formaldehyde reduced the presence of SVV1 in subsequent batches of feed intended for animal consumption and in the environment. Although the virus was still detectable in these samples via PCR tests, SVV1 infection was not observed when pigs were inoculated with these samples, meaning, the pigs did not get sick despite a miniscule amount of viral fragments remaining on the samples.  

Experiment 2: Conditioning and pelleting feed 

• This method of conditioning feed at 180°F for 30 seconds and pelleting, in other words, heating the feed up to a really high temperature and then pelleting the end product, reduced detectable SVV1 RNA in the pelleted feed product. Traces of genetic material were still present in the pelleted feed, but SVV1 infection was not observed when pigs were inoculated with pelleted feed samples. Once again, the pigs did not become sick despite trace amounts of viral fragments left in the final, heat-treated product. 

Experiment 3: Chemical or heat-based decontamination of equipment 

• Neither chlorine dioxide fumigation nor the application of heat significantly decreased the presence of SVV1 on the equipment or in the feed manufacturing environment as measured by PCR. In laymen’s terms, this method involved fumigating and/or heating the entire feed mill environment as opposed to simply treating the contaminated equipment, but it did not reduce the presence of viral fragments in the facility by much. However, pigs inoculated with samples from either treatment did not show signs of SVV1 infection.  

Concluding Observations 

SVV1, much like PEDV and ASFV, disseminates throughout a feed mill quickly following viral contamination of the feed. This contamination, if left unchecked, can increase the risk of product recontamination from residual virus contaminants in the feed or the environment, necessitating decontamination methods be used.  

The use of chemical flushes and pelleting reduces, but does not eliminate, SVV1 genetic material in

the feed or the environment. Similarly, SVV1 genetic material remained, following decontamination with either gaseous fumigation or portable heaters.  

Based on the PCR results alone, none of the tested methods completely removed all genetic material from the feed mill. All strategies used, however, reduced the risk of swine infection, given SVV1 infection was not observed in the bioassay.  

Ultimately, we saw that there is no “silver bullet” for the feed industry to use to fully decontaminate equipment or a facility, but the use of these methods showed some promising strategies that feed mills could consider implementing based on the conditions at their facility (e.g., equipment setup, access to personal protective equipment, workplace safety procedures, etc.).  

More information on this project, including the project conclusions and a feed mill biosecurity fact sheet, can be found on IFEEDER’s website. 

About the Authors: 

Olivia Harrison is a KSU Ph.D. candidate in animal sciences and industry at KSU. Chad Paulk, Ph.D., is a professor in KSU’s grain science and industry. Jordan Gebhardt, D.V.M. and Ph.D., is a professor in KSU’s diagnostic medicine and pathobiology. Jason Woodworth, Ph.D., and Cassandra Jones, Ph.D., are professors in KSU’s animal sciences and industry.