Feed and Feed Ingredients Are Not the "Big Stool Leg" Spreading Viruses to Pig Farms

Written by: Guest   |   August 29, 2022

African swine fever response, ag & food research, biosecurity, feed & food safety

By: Louis Russel, Ph.D., retired, APC
David Meeker, Ph.D., senior vice president of scientific services, North American Renderers Association
Leah Wilkinson, vice president of public policy and education, American Feed Industry Association

The issue

Montezuma’s Revenge.
Travelers’s diarrhea.
“Don’t drink the water.”

Who has not experienced an upset digestive system after eating or drinking something questionable? We all recognize that if food or water becomes contaminated with a pathogen, we can get sick after consuming it. It is the same for livestock. If the feed we deliver to the pig barn is contaminated with a virus, pigs could get sick after eating it. 

Over the past few years, there has been a lot of research documenting the potential for viruses to survive on different feed ingredients for extended periods of time. In addition, recent research demonstrates that if a contaminated feed ingredient is brought into a feed mill, dust from that ingredient sticks around and is likely to contaminate the feed mill itself, potentially contaminating even more feed.  

As a result, many in the industry were left wondering if potentially contaminated feed or feed ingredients represent a risk factor contributing to vast disease spread within the swine industry. Quantifying the actual risk in modern swine production systems is a critical next step in understanding how to mitigate the actual risk, and we needed to know the answer. 

The experiment

To quantify and prioritize the extent to which contaminated feed ingredients contribute to disease outbreaks in modern swine production systems, a group of industry organizations, including the Institute for Feed Education and Research (IFEEDER), North American Renderers Association (NARA) and North American Spray-Dried Blood and Plasma Producers (NASDBPP), jointly funded a research project at North Carolina State University (NCSU) to answer this question. Doctors Machado and Galvis, NCSU College of Veterinary Medicine, have been developing a mathematical algorithm that is able to analyze multiple risk factors and predict when a pig farm is most likely to break with a disease.

The industry organizations approached Dr. Machado and asked:

• Could the risk factors included in the model be expanded to include porcine-origin feed ingredients (e.g., meat and bone meal, choice white grease and spray dried porcine plasma) and feed delivery?
• Further, could the algorithm estimate the relative risk of each factor?

After some discussion, the experts concluded that the model could be expanded to include these additional risk factors and that since the model identified the risk factor that a particular disease break would be attributed to, the relative risk of each factor could also be estimated. The research team collected detailed data for approximately one year, including weekly disease status of porcine reproductive and respiratory syndrome virus (PRRSV) and porcine epidemic diarrhea virus (PEDv) of individual pig farms within a large pig dense region.  

The results

After collecting detailed information, the data was subjected to the algorithm, and the model predicted the most likely risk factor responsible for each disease outbreak. On average, 94% of the disease outbreaks were attributed to four risk factors, including:

• Local transmission, farm-to-farm proximity;
• Pig movement, between farms;
• Vehicles, pig movement between farms; and
• Vehicles, feed delivery.

Inclusion of porcine-origin feed ingredients were not among the high-risk events linked to the spread of PRRSV or PEDv.

Concluding observations

What have we learned?

It is very important that within all steps of the feed chain, beginning with ingredients, including transportation, milling, feed manufacturing and delivery, that sites of potential contamination are identified and procedures implemented that mitigate risks. However, in the modern swine production system studied in this research trial, porcine-origin feed ingredients were not identified as a big leg of the stool contributing to disease outbreaks (both PRRSV or PEDV).  Biosecurity protocols in place protected these ingredients from contamination. 

When designing biosecurity protocols, this data should be kept in mind, and biosecurity protocols should be focused on mitigating the risks attributed to 94% of disease spread.

The data highlights that because of regular feed deliveries to pig farms, feed delivery trucks represent a risk of spreading virus throughout the swine production system. It is also important to recognize that this data represents the risks associated with a particular system, reflecting a particular set of biosecurity practices. The data should not be extrapolated to all systems, which may include a different set of biosecurity practices.

Feed delivery is a necessary part of swine production. Therefore, future research should be conducted as to where and how feed trucks become infected and to help identify specific biosecurity practices to mitigate these risks. 

We encourage you to read more about the study here.