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03 Issues & Trends
Cereal Foods World, Vol. 65, No. 1
DOI: https://doi.org/10.1094/CFW-65-1-0008
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Foreign Animal Disease in the Feed Industry: What Are the Risks, and What Can We Do?1
Cassie Jones,2 Jason Woodworth,3 Steve Dritz,4 and Chad Paulk5,6

Kansas State University, Manhattan, KS, U.S.A.

1 Adapted from an article published in Feedstuffs, Vol. 91, No. 6, June 3, 2019.
2 Associate professor, Department of Animal Sciences and Industry.
3 Research professor, Department of Animal Sciences and Industry.
4 Professor, Diagnostic Medicine/Pathobiology.
5 Assistant professor, Department of Grain Science and Industry.
6 Corresponding author. E-mail: cpaulk@ksu.edu

© 2020 Cereals & Grains Association


Ingredients are just one of many potential routes for entry of foreign animal diseases (FAD) into the United States. U.S. regulatory agencies and other entities are taking steps to limit entry through more direct methods, but it is the responsibility of the feed industry to minimize the potential for FAD entry through feed transport vehicles. For FAD entry via an ingredient to occur, there needs to be an initial contamination event, virus survival during transport, and consumption of a virus at a dose capable of causing infectivity. Several ways in which swine feed manufacturers can minimize the potential for FAD entry and transmission via the feed supply chain are discussed. Although some mills are struggling to implement changes that maximize feed safety, the cost of FAD entry into a mill would be catastrophic. Therefore, we must adapt to make feed that is safe as well as wholesome.

As African swine fever virus (ASFV) continues to spread across Southeast Asia, Classical swine fever virus (CSFV) expands within Japan, and Foot-and-mouth disease virus (FMDV) continues to be reported from China, there is increased concern that foreign animal disease (FAD) may enter the United States. The entry of these diseases would be devastating to the U.S. swine industry, but also to those who produce feed and ingredients fed to pigs. In its May 2019 “Food Outlook” report (4), the Food and Agriculture Organization of the United Nations reported that pig feed sales were down 10–50% in the Guangdong Province of China and that pig feed production in Shandong Province was only 67% of the 2018 volume. In 2011, Dermot Hayes from Iowa State University estimated that revenue losses due to FAD entry into the United States would be $17.4 billion annually, mostly due to loss of export markets and lower corn and soybean usage.

Risks for FAD Entry through Ingredients

There are many potential routes for FAD entry into the United States, with ingredients being just one route. The U.S. Customs Border Patrol, U.S. Department of Agriculture, U.S. Food and Drug Administration, and other entities are taking steps to limit entry through the use of more direct methods, such as regulating the importation of live animals or smuggling of pork products, but it is the responsibility of the feed industry to minimize the potential for FAD entry through a feed transport vehicle. For FAD entry via an ingredient to occur, there would need to be an initial contamination event, virus survival during transport, and consumption of a virus at a dose that is capable of causing infectivity.

Contamination of an Ingredient. Reports of the presence of ASFV in feed are already occurring. The Ministry of Agriculture and Rural Affairs of the People’s Republic of China has reported that 22 of 68 reported ASFV outbreaks had an epidemiological root cause linked to contaminated swill or feed. It is likely that most of these outbreaks were due to swill feeding in transitional, backyard swine herds. However, there is evidence that ASFV contamination exists in ingredients used in modern production as well. Dee and Spronk reported at the 2019 American Association of Swine Veterinarians Meeting in March that 1–2% of tested ingredients from modern Chinese feed mills were ASFV-positive, including corn, soybean meal, rice, wheat, and dried distiller’s grains with solubles (DDGS).

Virus Survival during Transport at Concentrations Capable of Causing Infection. Theoretical survival of FMDV (via a Senecavirus A surrogate) and ASFV has been demonstrated by Dee et al. (3), while CSFV appears to be likely to survive transportation as well. Niederwerder et al. (9) recently reported that pigs consuming ASFV-contaminated feed can become infected when consuming a single 100 g meal of feed containing a single dose of ASFV (104 TCID50/g). By modeling this data, it is expected exposure of pigs to 30 meals containing a low dose of ASFV (100 TCID50/g) will lead to a significant probability of infection. Feed industry equipment and processes are designed to efficiently mix low-inclusion products uniformly throughout a batch of feed and then deliver feed in a method that provides multiple meals with the same consistency to many pigs housed in the same location. If ASFV or another FAD enters the feed supply chain and is mixed into a batch of feed, the results could be catastrophic contamination across multiple herds. For example, Schumacher et al. (11) reported that if 1 g of feces from an acutely infected pig with Porcine epidemic diarrhea virus (PEDV) entered a receiving pit, it could potentially contaminate 500 metric tons of feed, with each gram having a dose capable of causing infectivity. That is the equivalent of twenty 24 ton feed trucks, all carrying infectious material to different facilities. Simultaneously, the entry would cause contamination of the feed manufacturing equipment. In 2017, Schumacher et al. (10) reported that entry of PEDV into a feed mill leads to nearly 100% of surfaces being contaminated, including noncontact surfaces such as walls and floors. Subsequently, Gebhardt et al. (5) reported that material collected from these noncontact surfaces is capable of causing infectivity. Finally, Huss et al. (6) reported that the cleaning and disinfection necessary to sanitize a virus-contaminated feed mill includes complete removal of organic materials, followed by wet-cleaning with a glutaraldehyde disinfectant and then a bleach sanitizer. The U.S. feed industry is not designed for this type of cleaning and disinfection process, so the primary focus must be on keeping pathogenic viruses out of feed mills. This includes a focus on both the source of the ingredients and their transportation to the U.S. facility. The incubation period for ASFV is 5–21 days, and it may be up to 3 weeks after an animal is exposed before signs of the disease occur. During this time, the feed supply chain may be unknowingly transmitting the virus. Therefore, strenuous actions are necessary to prevent feed mills from being a source of cross-contamination.

Recommendations for Ways in which Swine Feed Manufacturers Can Minimize the Potential for ASFV and Other FAD Entry and Transmission via the Feed Supply Chain

  1. Know your supplier. It is key that facilities can identify the suppliers of the ingredients coming into their facility. This process helps maintain transparency across the feed supply chain. In some facilities, procurement is independent from quality control and feed safety. These functions need to be fully integrated, however, with a system for checks and balances to ensure that the most economical ingredients are used, but only if they are not a potential risk for disease entry. Knowledge of the ingredient supply chain should extend from the point of ingredient manufacture through transportation to the feed mill, including any intermediaries or blending locations.
  2. Do not use grains or oilseeds (or their resultant meals) from regions with FAD. Feed mills manufacturing feed for multiple species should follow this practice for the entire mill, not just exclude it from swine feed. For example, it has been reported that mills manufacturing feed for sow multiplication facilities are also manufacturing organic dairy feed, with imported organic soybean meal from China being used only in dairy feed. Because of the potential for batch-to-batch and environmental contamination, these high-risk ingredients should be excluded from the mill altogether.
  3. If using other ingredients from regions with FAD, take steps to ensure they are at low risk for disease transmission. The decision tree matrix to minimize viral transmission risk from feed ingredients produced by the Swine Health Information Center (www.swinehealth.org) and other leading swine organizations can aid in this assessment. In particular, consider both the point of manufacture and the method of transportation. It may be appropriate to have different procedures for receipt of ingredients transported in different forms. For example,

a.   If ingredients are delivered in bulk (vessel, barge, rail, or truck), require washout tickets or proof of low-risk loads since the previous washout prior to receipt.

b.   If ingredients are delivered in bulk tote bags, obtain proof that bags were not reused prior to loading and inspect the bags for damage prior to receipt.

c.   If ingredients are transported in small, single-use, sealed bags, sanitize the pallet, pallet jack, trailer floor, and any plastic wrapping prior to receipt. Inspect bags for damage prior to receipt and disallow the use of wooden pallets.

  1. Use porcine-based ingredients with caution. Porcine-based ingredient production is likely to contain a kill-step capable of destroying viruses. However, postprocessing cross-contamination may exist, creating the potential for these ingredients to be sources of virus entry into mills. If porcine-based ingredients are used, obtain these ingredients from suppliers with documented biosecurity procedures and programs to reduce the risk of postprocessing cross-contamination. If there is concern about ASFV or CSFV, other animal protein ingredients can be used with negligible risk. If the concern extends to FMDV, ensure that all suppliers of animal proteins have adequate programs to address biosecurity and postprocessing contamination.
  2. Implement biosecurity at the mill. Biosecurity procedures have been in place for decades on swine farms to limit disease transmission by people and delivery vehicles. These same principles should be extended to mills.

a.    Develop a feed mill biosecurity plan. Methods for developing a swine feed mill biosecurity plan are described by Cochrane et al. (2). Other references, such as the American Feed Industry Association guide for “Developing Biosecurity Practices for Feed & Ingredient Manufacturing” (1), and the Kansas State University “Swine Feed Mill Biosecurity Audit” (7), are helpful for facilities to determine opportunities for improving biosecurity.

b.   Use receiving mats or funnels to limit pathogen entry into the receiving pit. The ingredient receiving pit is the single biggest entry point for contaminants into the feed manufacturing system. Magossi et al. (8) reported that the pit was second to only employee shoes as the most unhygienic locations tested in 12 U.S. feed mills.

c.    Create lines of separation at all doors to minimize contamination from footwear. This involves employees and visitors changing shoes to keep exterior shoes on one side of the line and interior shoes on the other. Examples of how facilities may implement lines of separation are shown in Figure 1. In both examples, additional exits are available in case of emergency to satisfy U.S. Occupational Safety and Health Administration (OSHA) requirements. If lines of separation cannot be developed, consider zoning to standardize traffic patterns, with foot baths or food-grade dry sanitizing powder placed in high-traffic areas.

d.   Create cleaning and disinfection stations for delivery vehicles and feed trucks. Use wet-cleaning and sanitizers to remove debris from the tires, wheels, undercarriage, and exterior of ingredient and feed delivery trucks prior to their entry into the mill. This is particularly pressing during times when disease pressure is high. Be sure that all vehicles are rinsed and dried prior to entry into the mill to prevent cleaners or sanitizers from being a source of contamination themselves.

e.    Sanitize floors routinely. Sweep or vacuum all dirt and dust from floors and then mop on a weekly basis to limit the accumulation and spread of virus on non–feed-contact surfaces. Mopping material should be a bleach solution with at least 2.3% chlorine or a U.S. Environmental Protection Agency-approved FAD disinfectant, such as a solution with at least 1% VirkonTM S.

f.     Refrain from using dust, screenings, or similar materials as an ingredient or adding them back into feed production. These materials are frequently added back into ground corn or an ingredient bin to minimize shrink. However, dust is consistently reported to carry high levels of pathogens and should be composted or discarded, never fed to animals.

  1. When delivering feed, use cleaning and disinfection stations prior to entering and exiting farms. Alternatively, consider unloading feed across a line of segregation or fence into another feed truck, or extend bin augers so bins can be filled on the exterior of the line of segregation, as shown in Figure 2.

We are in a new era of feed production, where feed safety is just as paramount as quality and tonnage. Unfortunately, some mills struggle to implement changes that maximize feed safety, because it is difficult to establish a return on investment (ROI) calculation for the extra effort. Still, the cost of FAD entry into a mill would be catastrophic, and therefore, we must adapt our culture to make feed that is not just wholesome, but also safe.


  1. American Feed Industry Association. Developing biosecurity practices for feed and ingredient manufacturing. Published online at www.afia.org/pub/?id=E348BF9F-98ED-09DB-A45D-504737FE7AE2. AFIA, Arlington, VA, 2019.
  2. Cochrane, R. A., Dritz, S. S., Woodworth, J. C., Stark, C. R., Huss, A. R., Cano, J. P., Thompson, R. W., Fahrenholz, A. C., and Jones, C. K. Feed mill biosecurity plans: A systematic approach to prevent biological pathogens in swine feed. J. Swine Health Prod. 24:154, 2016.
  3. Dee, S. A., Vauermann, F. V., Niederwerder, M. C., Singrey, A., Clement, T., et al. Survival of viral pathogens in animal feed ingredients under transboundary shipping models. PLoS One. DOI: https://doi.org/10.1371/journal.pone.0194509. 2018.
  4. Food and Agriculture Organization of the United Nations. 2019 Food outlook—Biannual report on global food markets. Published online at www.fao.org/3/ca4526en/ca4526en.pdf. FAO, Rome, Italy, 2019.
  5. Gebhardt, J. T., Cochrane, R. A., Woodworth, J. C., Jones, C. K., Niederwerder, M. C., et al. Evaluation of the effects of flushing feed manufacturing equipment with chemically treated rice hulls on porcine epidemic diarrhea virus cross-contamination during feed manufacturing. J. Anim. Sci. 96:4149, 2018.
  6. Huss, A. R., Schumacher, L. L., Cochrane, R. A., Poulsen, E., Bai, J., Woodworth, J. C., Dritz, S. S., Stark, C. R., and Jones, C. K. Elimination of porcine epidemic diarrhea virus in an animal feed manufacturing facility. PLoS One. DOI: https://doi.org/10.1371/journal.pone.0169612. 2017.
  7. Kansas State University. Swine feed mill biosecurity audit. Available online at www.asi.k-state.edu/research-and-extension/swine/FeedSafetyResources.html. KSU, Manhattan, KS, 2018.
  8. Magossi, G., Cernicchiaro, N., Dritz, S., Houser, T., Woodworth, J., Jones, C., and Trinetta, V. Evaluation of Salmonella presence in selected United States feed mills. MicrobiologyOpen. DOI: https://doi.org/10.1002/mbo3.711. 2018.
  9. Niederwerder, M. C., Stoian, A. M. M., Rowland, R. R. R., Dritz, S. S., Petrovan, V., et al. Infectious dose of African swine fever virus when consumed naturally in liquid or feed. Emerg. Infect. Dis. 25:891, 2019.
  10. Schumacher, L. L., Huss, A. R., Cochrane, R. A., Stark, C. R., Woodworth, J. C., et al. Characterizing the rapid spread of porcine epidemic diarrhea virus (PEDV) through an animal food manufacturing facility. PLoS One. DOI: https://doi.org/10.1371/journal.pone.0187309. 2017.
  11. Schumacher, L. L., Woodworth, J. C., Jones, C. K., Chen, Q., Zhang, J., et al. Evaluation of the minimum infectious dose of porcine epidemic diarrhea virus in virus-inoculated feed. Am. J. Vet. Res. 77:1108, 2016.