Characterization and Description of Alternative Pig Farms in Minnesota

Final report for GNC22-352

Project Type: Graduate Student
Funds awarded in 2022: $14,934.00
Projected End Date: 12/31/2023
Grant Recipient: University of Minnesota
Region: North Central
State: Minnesota
Faculty Advisor:
Dr. Cesar Corzo, DVM, MSc, PhD
University of Minnesota
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Project Information


Practices for managing pig health within the United States (US) swine industry have evolved from backyard pig production circa World War II; pig production is now characterized by raising age-segregated pigs indoors in large premises. Despite this shift, there are still farmers who have chosen to raise their pigs in alternative settings, most notably, with outdoor access. Alternative pig farms (APFs) include, but are not limited to, those labeled as niche, pasture-raised, US Department of Agriculture (USDA) organic-certified, heritage breed, purebred, regenerative, and humane-certified 1. The demand for pork produced by APFs is increasing as consumers are continuing to seek pork that has been with produced with alternative productive production to those of conventional production practices2.

Unfortunately, despite the perceived benefits of alternative production practices, APF pigs may be at a higher risk of a variety of disease-causing pathogens due to their exposure to the natural environment. Pigs on APFs do have a higher likelihood of encountering wild animals who could potentially transmit infectious diseases or parasites to the pigs. Additionally, these risks may continue even after the life of the pig because contaminated meat products could potentially infect both humans and other animals including pigs. Although pigs raised conventionally may face these same risks, they can better mitigate them through the mechanical, chemical, and physical barriers of their confinement. However, these barriers may not apply to APFs due to the unique and diverse production/management, veterinary use, biosecurity, and marketing methods.

Therefore, effort needs to be made to better understand these practices so that appropriate preventative health practice recommendations can be made that are specific to this population. Especially as these farms may exist not only to serve for pork production, but also aid in creating a more robust local food system or utilize their pigs for regeneration of the environment. The objectives of this project include 1) characterize and describe Minnesota (MN) APFs, 2) estimate disease prevalence in APFs, and 3) identify farming practices that increase odds of disease.

To characterize and describe APFs in MN, over 200 farms that raise pigs with outdoor access were identified and subsequently emailed an online Qualtrics® (Provo, UT) survey in December 2022-Decembe 2023 that included questions regarding their farming and management, biosecurity, and marketing practices of their pig herd. A prevalence study was performed for the presence and previous infection with Porcine Reproductive and Respiratory Syndrome Virus (PRRS), the presence of three enteric porcine enteric coronaviruses: Porcine Epidemic Diarrhea Virus (PEDV), Transmissible Gastroenteritis Virus (TGEV) and Porcine Deltacoronavirus (PDCoV), and for previous infection with Pseudorabies Virus (PRV) which is the causative agent of Aujesky’s disease.

Both PRRSV and the porcine enteric coronaviruses (PECs) are endemic diseases in conventional pig farms. PRRSV can cause high abortion rates in breeding herds and morbidity in grow-to-finish herds due to respiratory disease, whereas the PECs can cause high morbidity in all ages due to gastroenteritis. In addition to the welfare implication this has for pigs, it can also cause severe economic losses in CPFs but are of unknown prevalence in APFs. PRV has been eradicated from domestic swine in the US, but does exist in feral populations, for which pigs with outdoor access are at higher risk of infection. Logistic regression was performed using variables from the survey and the outcome of disease from the prevalence study to identify any farming practices that increase odds of these diseases, for which mitigation could then be pursued on the farm.

The results of this survey provide information on the different production, management, veterinary medicine usage, biosecurity, and marketing practices of farms in MN that raise pigs with outdoor access and/or are considered “alternative”. Due to the increasing demand for pork produced by APFs, the information gathered from the survey has identified a few practices that should be further explored, to evaluate their role in the spread of disease, and how they may be improved to decrease the spread of disease.

Researchers were able to better understand the barriers APF farmers may face against the utilization of veterinarians and on-farm veterinary care. Over 1/3 of survey respondents have never consulted with a veterinarian, either because their pigs were healthy or because they didn’t have access to a veterinarian who is knowledgeable in swine medicine. Therefore, education thus far has focused on the veterinary industry, as we believe this will have the greatest impact on changing the attitudes for all those involved in the care of pigs raised on APFs. A presentation focusing on areas of improvement for the veterinary industry from the survey results was presented to the American Association of Extension of Veterinarians and a poster presentation was given at the American Association of Swine Veterinarians that highlighted the farm demographics and farming, management, and biosecurity practices of survey participants.

All prevalence study participants were compensated with $150 which they were encouraged to use towards any existing or future veterinary care. Sampling and diagnostic testing was provided free of charge, and we worked to connect the farms with veterinarians if they wanted. We hope to disseminate the key findings of the survey along with recommendations for on-farm practices to improve pig health emailed directly to participants and other APF farmers via association newsletters, extension publications, and peer-reviewed publications.

From the prevalence study, there were no farms that tested positive for PRV or any of the PECs. It is possible that PECs were not found in this population because the housing environment of APFs may limit its spread and/or the survivability of the virus. Regardless, PECs do not seem to be a disease of concern in this population. Of the 25 farms that were tested for PRRSV, 36% of farms showed evidence of previous infection and 20% tested positive for the presence of the virus at the time of testing. Although this prevalence is comparable to conventional pig farms, risk factor analysis suggests that APFs with hoop barns may have a higher odd of being infected with PRRSV. In addition to on-farm practices, how these APFs interact with each other, such as pig movement or location of their farm in relation to another, can also play a role in disease spread. Therefore, additional research should be performed to evaluate the extent to which this population interacts with each other, the broader swine industry, and the impact this could have on disease spread.

  1. Certified Humane - A Project of Humane Farm Animal Care. Accessed July 4, 2022.
  2. Sato P, Hötzel MJ, Von Keyserlingk MAG. American citizens’ views of an ideal pig farm. Animals. 2017;7(8). doi:10.3390/ani7080064
Project Objectives:

Objective 1: Characterize and describe Minnesota (MN) APFs.

Results from the survey will provide information for four farm practice areas in: 1) Production/Management, 2) Veterinary Use, 3) Biosecurity, and 4) Marketing. The information gathered in this study can be used to better understand the APFs’ role in the ecology of infectious disease and identify specific practices for which established disease prevention and control measures can be adapted for this population, ultimately improving pig health.

Objective 2: Estimate PRRS, PECs, and PRV pathogen prevalence in APFs.

Establishing the baseline for which disease prevalence exists in APFs will not only allow us to assess the degree to which the disease exists in the population but will allow us to have a metric when comparing this population to others (such as convention pig farms), and to future prevalence studies following intervention applications. Pathogens that are pig specific and are endemic in conventional pig farms will be tested for, along with one disease that has been eradicated from domestic pigs in the US but can be found in the feral pig population.

Objective 3: Identify farming practices that increase disease risk.

It is expected that general farming practices will differ on APFs from conventional pig farms, therefore, it may be that the practices that may lead to increased risk to disease on conventional farms may not be the same practices that lead to increased risk to disease on APFs. Therefore, the last objective of the project is to identify any practices that lead to an increased risk, or increased odds, of disease. This is turn, will identify practices that can be improved and mitigated to decrease disease in the future. Using the survey results and the prevalence study diagnostic test results, logistic regression can be performed to calculated Odds Risk Ratio for variables that are identified to have an association with the outcome of a positive test and are statistically significant.


The aim of this study was to describe and characterize four areas of practice of APFs in MN: 1) Production/Management, 2) Veterinary Use, 3) Biosecurity, and 4) Marketing, calculate disease prevalence, and identify any practices that may lead to an increase in the odds of disease infection. The information gathered in this study can be used to better understand the APFs’ role in the ecology of infectious disease and identify specific practices for which established disease prevention and control measures can be adapted for this population, ultimately improving pig health and ensure the longevity of this type of pig production.

Problem 1: Current knowledge of APF practices in US is lacking.

Unfortunately, there is little published information about APF practices in the US within the context of veterinary medicine or swine health and production. The literature that does exist is outdated, non-specific, or only captures information on one type of APF. Additionally, niche and organic pig production is much more common in Europe with a variety of research reports available regarding this type of pig production. Yet, the information on their practices seems to be country specific and may not be as applicable to US APF production, especially within the context of the respective country’s laws, regulations, or culture. As the demand for pork produced by APFs is increasing in the US2, knowledge on the current practices of these farms will be important to have, especially for the veterinary and swine industry.

Problem 2: Unknown Disease Prevalence for PRRS, PECs, and PRV.

There is a published report on the health challenges in midwestern niche pork 3, and a survey of disease pressures in twenty-six niche herds 4, but these were limited in scope to niche pork producers under contract with three midwestern marketing companies. Additionally, there was a survey of disease prevalence for pigs in Hawai’i, but this population itself differs from that of APF production found in MN and the Midwest. An updated disease prevalence for PRRS (20%), PECs (0%), and PRV (0%), was able to be estimated from this project that is specific to the APF population in MN.

Problem 3: Factors that increase disease risk for APFs are unknown.

Due to the generally different practices employed by APFs, the factors that may lead to increased disease risk for these farms may be different than what has been historically established for conventional pig farms. Differences in practices that were identified included housing, genetics, farm type, herd size, biosecurity, veterinary use, and marketing. Using the results from the survey and prevalence study factors were identified that may lead to an increase in disease risk for APFs. Specifically, the use of hoop barns may lead to an increase in disease risk for PRRSV, and the use of a farm specific vehicle may lead to a decrease in disease risk for PRRSV. The project also identified variables for which can be further researched for association of risk such as location.

  1. Sato P, Hötzel MJ, Von Keyserlingk MAG. American citizens’ views of an ideal pig farm. Animals. 2017;7(8). doi:10.3390/ani7080064
  2. Layman L, Yaeger M, Karriker LA. Health Challenges in Midwestern “Niche” Pork Production Systems. Iowa State Univ Anim Ind Rep. 2008;5. doi:10.31274/ans_air-180814-732
  3. Yaeger MJ, Karriker LA, Layman L, Halbur PG, Huber GH, Hulzen KV. Survey of disease pressures in twenty-six niche herds in the midwestern United States. J Swine Health Prod. 2009;17(5):8.


Click linked name(s) to expand/collapse or show everyone's info
  • Dr. Sarah Chagas (Researcher)
  • Dr. Marie Culhane (Educator and Researcher)
  • Dr. Valeria Lugo (Researcher)
  • Dr. Eliana Paladino (Researcher)
  • Dr. Miqueias Vargas (Researcher)


Materials and methods:

Characterize and describe Minnesota (MN) APFs.

To characterize and describe MN APFs, a survey was conducted to collect information from this population in four practice areas 1) Production/Management, 2) Veterinary Use, 3) Biosecurity, and 4) Marketing.

  1. Study population: The population was identified from publicly accessible databases that fit the study definitions for APFs (i.e., those that raise pigs with outdoor access, sell pigs and/or pork for income, and are located in MN or the surrounding states but do business in MN; outdoor access refereed to those housed in hoop barns with deep bedding or with access to grass pasture, dirt lots, and/or concrete runs outside the confines of an enclosed building).
  2. Survey development: The survey was created using Qualtrics® (Provo, UT) and adapted from a farm characteristic questionnaire to identify risk factors for Senecavirus A in US pig farms5.
  3. Survey dissemination: The survey was emailed directly from Qualtrics® to the identified APFs. The survey link was made also make public and was sent to various farm and agricultural organizations to be disseminated via their member newsletters and via the UMN Swine Extension podcast to recruit additional participants. While recording responses, if any veterinarians were named, the veterinarians and clinics were contacted to ask them to disseminate information about the survey to their other clients. Finally, farms that had not responded to the survey were contacted by phone asking them to participate and emailed the survey again.
  4. Participation: The survey was estimated to take 30 minutes to complete, participants could start the survey and come back to the survey later, the survey could be anonymous, and they were allowed to either skip a question or choose to “prefer not to answer”. Finally, participants were offered a $25 gift card for the completion of the survey.

Estimate PRRS, PECs, and PRV pathogen prevalence in APFs.

To estimate pathogen prevalence in APFs for PRRS, PECs, and PRV, we collected biological samples from the pigs from a subset of farms that completed in the survey.

  1. Recruitment of prevalence study participants was made by advertising the project as a question in the survey and asking survey participants for their contact information if they were interested in participating. Additional participants were chosen by cold-calling farms that had not responded to the survey or were chosen from farmers who had reached out to us with interest in participating.
  2. This was a cross-sectional study where samples were collected from March 2023 to December 2023 and farms were only visited once for each of the 24 farms. The presence of PRRSV RNA via RT-PCR was tested in either serum or oral fluids at the University of Minnesota Veterinary Diagnostic Laboratory (UMN VDL). Serum samples were tested in pools of two to five. Any farm that had at least one positive RT-PCR test was classified as a positive herd. The presence of PRRSV antibodies via ELISA, indicating previous infection was also tested for in serum either individually or in pools of two to five, or in oral fluids. Any farms that were positive via ELISA but not RT-PCR indicated further evaluation. The presence of PECs (PEDV/TGE/PDCoV) RNA via RT-PCR was tested in oral swabs or oral fluids. Any farm that had at least one positive RT-PCR test was classified as a positive herd. The presence of PRV antibodies via serum neutralization (SN) was tested in serum. Any farm that had at least one positive PRV SN was classified as a positive herd.
  3. To encourage participation, farms did have the option to only have oral fluids collected rather than blood collected from their pigs for testing, as a more “hands-off” method of sample collection from their herd, and to opt-out of having their herd tested for PRV, which is a federally regulated disease (that if test positive, would initiate a federal disease investigation). To encourage chewing behavior of the pigs on the cotton ropes for oral fluid collection, farmers had the choice of using organic agave syrup (as opposed to non-USDA certified organic vanilla pudding). Additionally, there was one farm that had testing performed by their personal herd veterinarian previously, whose results were included in the final disease prevalence estimation. Finally, all disease prevalence study participants were compensated with $150, and encouraged to use this towards any current or future veterinary care.

 Identify farming practices that increase disease risk.

To identify any farming practices that increase disease risk, both the results of the survey and the test outcomes from the disease prevalence study were used in logistic regression.

  1. Measures of association were calculated, and p-value assessed to determine statistical significance using the practices evaluated in the survey as the dependent variable and the PRRSV test outcome, as the binary outcome of interest. Due to the small sample sizes non-parametric tests were used: fisher’s exact test was used for categorical variables and Kruskal-Wallis test used for continuous variables.
  2. Variables that had a p-value of <1 were further evaluated using univariable logistic regression, where these variables were the dependent variable and the PRRSV test outcome, as the binary outcome of interest. Odds risk ratio was calculated for these variables and their p-value assessed on <0.05.


  1. Preis G, Sanhueza JM, Vilalta C, Vannucci FA, Culhane MR, Corzo CA. Senecavirus A seroprevalence and risk factors in United States pig farms. Front Vet Sci. 2022;9. Accessed June 6, 2023.
Research results and discussion:

APF Practice Survey Results:

We identified 200 APFs in MN and received 57 survey responses (29% survey response rate). Five of the farms were located in Wisconsin, one was in Illinois, and 51 in MN.

As expected, there were many differences identified between conventional pig farms and APFs that included farm type, herd size, genetics, housing, breeding methods, veterinary use, biosecurity, and marketing. Especially the establishment of on-farm biosecurity plans, the implementation of biosecurity practices, and access to veterinary care.

A few notable results for which practices differ from conventional farms include:

61% of survey respondents were farrow-to-finish farms and 37% were grow-to-finish or wean-to-finish.

Grow-to-finish and wean-to-finish farms had a median of 13 pigs with a minimum of 4 and a maximum of 460. Farrow-to-finish farms had a median of 6 sows with a minimum of 1 and a maximum of 90 and a median of 2 boars with a minimum of 1 and a maximum of 10.

72% of breeding herds used natural breeding.

64% of respondents had pasture/forest access and 5% exclusively used hoop barns with deep bedding.

13% produce their own feed on-site.

45% have never consulted a veterinarian.

93% produce other livestock/poultry.

32% have double perimeter fencing.

Only 19% have employees (that do not live on-site).

2 farms exclusively utilize USDA-exempt meat lockers.

84% sell pork direct to consumers.

10% report implementing zero biosecurity measures, and out of the 12 biosecurity measures listed, 57% implement less than five.

Only 1/3 of farmers have a specific biosecurity plan, this may be an area in which APFs can focus their attention for disease prevention. Creating a plan could be a helpful exercise to evaluate what additional measures may be feasibly implemented on their own farm.

Estimated prevalence for PRRSV, PECs, and PRV in APFs:

There were no herds that tested positive for the PECs or for PRV. There were 23 farms that had samples collected for PRRSV as part of this study and two farms that sent results to the research team from previous testing for PRRSV that had been performed by their own veterinarian between December 2022-July 2023, for a total of 25 farms included in PRRSV prevalence estimation. Thirty-six percent of herds (9/25) had at least one positive ELISA test, indicating previous infection with PRRSV, and 20% (5/20) had at least one positive RT-PCR test, indicating the current presence of PRRSV RNA. All herds that were positive via RT-PCR also had at least one positive ELISA test, leaving four farms that were positive via ELISA but not RT-PCR. These farms will require further evaluation, such as individually testing pigs from the pooled sample and evaluating via immunofluorescence antibody (IFA) to rule-out false-positive results, since IFA has a higher diagnostic specificity. Additionally, this a true prevalence will need to be estimated adjusting for misclassification from using imperfect diagnostic tests.

Overall, it seems that although PRRSV does exist in APFs, but maybe not the extent that it exists in conventional pig farms. The third objective focused on identifying farming practices that may lead to an increased disease risk for PRRSV. There were also no herds that tested positive for PECs. These viruses are spread in contaminated feces, and in conventional farms, the spread may be perpetuated due to manure management practices. In APFs, this may not be as big of a problem, and due to the open housing environment of these herds it’s possible that the viruses become inactivated. More research specific to understanding the epidemiological spread of PECs, and more broadly gastrointestinal pathogens, is needed specific to APFs. Finally, there were no farms that tested positive for PRV. This is both a federally reportable, and MN state reportable porcine disease. Generally, it is a pathogen of feral pigs in the US, but has occasionally been confirmed in domestic pigs, especially those whose housing places them in close contact with potentially infected feral swine. There are no known established feral swine colonies in MN, putting APFs in MN at even lower risk for infection of disease, but it can be expected that there are some breeding swine that have been purchased from other states that do have established feral swine colonies. Further assessment of other diseases that seem to be of higher importance to APFs should also be identified and researched.

Identified farming practices that may increase disease risk:

Analysis for the identification of farming practices that may increase PRRS disease risk was limited by sample size. There were two practices that were identified as having an association with a positive PRRSV ELISA test: use of a farm specific vehicle (p=0.08) and housing including a dry-lot (p=0.027). Housing including hoop barns showed evidence of having an association with a positive PRRS RT-PCR test (p=0.038). Odds risk ratio (OR) was then calculated using univariable logistic regression for these three practices. Dry-lot housing had a problem with collinearity and was unable to have an OR calculated. Farm specific vehicle had a calculated OR of 0.015 (CI95% 0.020-1.08) indicating a potential protection against PRRSV infection, although there is a wide CI that crosses over past an OR of 1.0. Hoop barn housing had a calculated OR of 13.5 (CI95% 1.34-135.98) indicating a potential risk with the use of hoop barns, although there is a wide CI, but OR was above 1.0.

Despite the wide confidence interval, further assessment of the specific practices of farms that use hoop barns may be warranted. Potential reasons that hoop barns may put pigs at higher risk of infection with PRRSV may relate back to how the virus is spread. PRRSV is a respiratory pathogen, and hoop barns with deep bedding may have less ventilation when compared to herds that are not housed in hoop barns. Another possibility is stocking density. Hoop barns may allow for an increased stocking density in that area, making it easier for the virus to spread within the herd. Although herd size did not show any evidence of being associated with a positive ELISA (p=0.76) or RT-PCR (p=0.28). Finally, there were other variables that are known to increase risk for PRRSV in conventional pig farms, that were not evaluated for APFs. This includes location of the farm, specific to the proximity to other pig farms, and/or the density of pigs within a given area. It is possible that the location of the APF may increase risk to infection with PRRSV.

Participation Summary
59 Farmers participating in research

Educational & Outreach Activities

2 Consultations
2 Published press articles, newsletters
2 Webinars / talks / presentations

Participation Summary:

80 Ag professionals participated
Education/outreach description:


Funding provided the opportunity for two farms to have necropsies and veterinarians perform a herd health check on their farm when their herd presented with a pig health emergency. Not only did they have the funding provided, but this also helped provide data for my research, but also connected them with a veterinarian that they are able to reach out to for future pig herd health consultations.

Published articles, newsletters:

There have been two published newsletters targeted towards conventional pig producers that have been published with results of the survey and the prevalence study. 

Webinars, talks, presentations:

One oral presentation was given at the American Association of Extension Veterinarians focused on the results of the survey and how extension veterinarians can better serve this population. One poster presentation was given at the American Association of Swine Veterinarians focused on the results of the survey to make the practices of these farms more transparent to swine veterinarians. 

Project Outcomes

1 Grant received that built upon this project
Project outcomes:

The survey has highlighted the need for education of farmers on the topic of biosecurity. Although this project did not specifically focus on farmer education, it did identify focus areas for future education. Only 1/3rd of surveyed farms have farm-specific biosecurity, and the majority of those farms only implement five or less of the 12 listed biosecurity measures. Additionally, there were eight farmers that were unsure whether their farm had a registered premises identification number, which is important for traceability efforts. These are all areas in which education can be focused in the future to improve the overall health and wellbeing of alternatively raised pigs.

This project has allowed us to characterize and describe APFs in MN and estimate their PRRS, PECs, and PRV prevalence. Results from the prevalence study were shown to veterinarians and producers of conventional pig farms, and highlights of the survey were given to extension and swine veterinarians. Presenting these results made the practices of APFs more transparent to the broader swine and veterinary industry, hopefully making it easier for the two populations (conventional and alternative) to connect and find areas of synergy and harmonization for the betterment of all.

Twenty-four farms were provided with free sample collection and diagnostic testing for their pig herd. We were also able to assist two farmers in connecting them with veterinary care and arrange for necropsies to be performed at the UMN VDL for pigs in their herd. When coordinating this veterinary care. it became obvious that there is a lack of access to veterinary care in these farmer’s regions. This was also confirmed after speaking with other farmers who mentioned that although they have veterinary care for other animal species on their farms, these veterinarians do not provide care for pigs. Although this may not be the case in regions with high concentrations of pig farms (including conventional farms), additional work needs to be done within the veterinary sector to address this deficit. There are many professional veterinary organizations and associations that could spearhead initiatives to improve these conditions, and information from this survey should be helpful in their efforts.

Knowledge Gained:

Traditional diagnostic sample collection for this population was difficult, especially if the farms did not have the equipment or facilities to handle the pigs for blood collection. Oral fluid collection was also difficult because chewing behavior of these pigs was also different from pigs in conventional housing. Cotton ropes used for oral fluid collection were required to be dipped in some sort of sticky sweet treat (i.e., vanilla pudding, marshmallow fluff, or agave syrup) to attract the pigs to the rope. Even with these enticements, some pigs were uninterested and no sample obtained. The field experience from this project made it obvious that if sample types required for conventionally raised pigs in confinement are going to be also required from APF pigs in outdoor pens, then both the appropriate number of personnel and transportable/temporary facilities need to be provided for these farms. Another potential solution would be the use of other non-traditional sample type collection that is easier in this housing environment.

The open sharing of information by APF farmers, whether it be to other farmers or even to the public, makes these farmers a welcoming community. As part of this project, I attended various conferences targeted towards farmers engaged in organic or sustainable farming practices. At one of these conferences, I was able to attend a presentation by a project participant that was all about their experience with raising pigs. Additionally, throughout this study, there were many farmers that posted videos and/or photos to social media of the research team collecting samples on their farm and advertised their participation in the research project and encouraged participation from other farms. This open sharing and participation of farmers in the farmers in the project has shown a willingness to learn and work with veterinarians. This highlights the need for more mediated conversations between APFs and veterinarians to better assess and serve the veterinary needs of this population.

Information Products

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.