# Free Range [Pig Farming](/knowledge/animal-farming/swine/pig-farming-breeding-farrowing-nursery-grow-finish-nutrition-and-biosecurity): Regulations, Housing, and Welfare ## Key Takeaways - Free-range pig farming necessitates adherence to specific regional regulations (e.g., UK's Welfare of Farmed Animals Regulations, NZ's Animal Welfare Code of Welfare 2018) and certification standards that mandate continuous outdoor access, defined stocking densities (typically 20-50 pigs/hectare), and provision of adequate shelter, shade, and wallows for thermoregulation. - Housing options include movable huts for pasture rotation to mitigate parasite buildup and soil degradation, and fixed shelters requiring rigorous cleaning and disinfection; both must offer protection from predators, extreme weather, and disease vectors. - Health management in free-range systems requires an integrated approach to combat increased risks of parasite exposure (e.g., gastrointestinal parasites documented in Romanian studies), disease transmission from wildlife (e.g., HPAI H5N1 transmission in multi-species farms), and conditions like osteochondrosis, which studies indicate may be more frequent than in confined settings. - Biosecurity is paramount, involving robust perimeter fencing to exclude wildlife, strict entry controls, vehicle disinfection, quarantine protocols for new animals, and diligent internal hygiene measures to prevent disease spread, particularly relevant given documented influenza virus circulation patterns in Spanish free-range farms. - Effective pasture management, including appropriate stocking density, regular rotation (7-21 days), and potential renovation, is crucial for maintaining soil health, controlling parasite life cycles, and ensuring adequate nutrition, while accurate record-keeping of stock movements, health treatments, and pasture use is essential for compliance and traceability. --- Free range pig farming involves keeping pigs with continuous access to outdoor pasture or paddocks, subject to specific regulatory definitions, housing requirements, and welfare standards that differ from confined systems. This article provides pig farmers transitioning to or optimizing free-range production with the regulatory framework, outdoor housing design options, and welfare considerations necessary for compliance and herd health management. ## At a Glance: Free Range Pig Farming Overview | Aspect | Key Requirement | Common Consideration | |--------|----------------|---------------------| | Stocking density | Defined by regional regulations, typically lower than confined systems | Pasture carrying capacity varies by soil type, climate, and season | | Outdoor access | Continuous access to pasture or paddocks during appropriate weather | Shelter, shade, and wallows must be provided for thermoregulation | | Housing | Movable huts or fixed shelters with bedding | Protection from predators, extreme weather, and disease vectors | | Biosecurity | Perimeter fencing, quarantine protocols, wildlife contact prevention | Free-range systems face higher disease exposure risks | | Welfare monitoring | Regular health checks, lameness scoring, parasite management | Osteochondrosis may be more frequent in free-range pigs | | Record keeping | Stock movements, health treatments, mortality, pasture rotation | Required for certification and traceability | ## Regulatory Definitions and Certification Requirements Free range pig farming is defined by regulatory bodies and certification programs that specify minimum standards for outdoor access, stocking density, and housing. These definitions vary by jurisdiction but share common principles of providing pigs with continuous access to pasture or paddocks. ### Legal Definitions by Region In the United Kingdom, free range pig farming is regulated under the Welfare of Farmed Animals (England) Regulations and certification schemes such as Red Tractor and RSPCA Assured. These require pigs to have continuous access to outdoor runs or pasture during daylight hours, with minimum space allowances per pig. The UK Department for Environment, Food and Rural Affairs (DEFRA) provides specific guidance on stocking rates, shelter requirements, and record keeping for free-range systems. In New Zealand, free range pig farming is defined under the Animal Welfare (Pigs) Code of Welfare 2018, which mandates that pigs must have access to outdoor areas with adequate shelter, shade, and wallows. The New Zealand Pork Industry Board operates a certification program that requires compliance with specific free-range standards, including minimum space allowances and pasture management practices. In the United States, free range pig farming is not federally defined but is regulated under state-level animal welfare laws and third-party certification programs such as Animal Welfare Approved and Certified Humane. These programs require pigs to have continuous access to pasture with minimum space allowances and specific housing and management practices. The USDA Agricultural Research Service provides research on animal production and protection systems relevant to free-range management (USDA ARS, www.ars.usda.gov/animal-production-and-protection). ### Certification Program Standards Certification programs for free range pig farming typically include requirements for: - Stocking density: Maximum number of pigs per hectare of pasture, often ranging from 20 to 50 pigs per hectare depending on soil type and climate - Outdoor access: Continuous access to pasture during appropriate weather conditions, with exemptions for extreme weather or veterinary treatment - Housing: Movable huts or fixed shelters with adequate bedding, ventilation, and protection from predators - Feed and water: Access to appropriate feed and clean water at all times - Health management: Preventive health programs, parasite control, and veterinary care - Record keeping: Documentation of stock movements, health treatments, mortality, and pasture rotation Farmers should verify the specific requirements of their target certification program before transitioning to free-range production. ## Outdoor Housing Design and Infrastructure Outdoor housing for free range pigs must provide protection from weather extremes, predators, and disease vectors while allowing pigs to express natural behaviors. Housing design directly affects pig welfare, productivity, and disease risk. ### Movable Huts and Arks Movable huts, also known as arks, are the most common housing type for free range pig farming. These lightweight structures can be moved to fresh pasture as needed, reducing parasite buildup and soil degradation. Key design considerations include: - Size: Huts should provide adequate space for all pigs to lie down comfortably, typically 1.5 to 2 square meters per sow or 0.5 to 1 square meter per grower pig - Insulation: Roof and wall insulation helps maintain appropriate temperatures inside the hut - Ventilation: Adjustable vents or openings allow airflow while preventing drafts - Flooring: Solid floors with deep bedding provide comfort and warmth - Access: Doors or openings should allow easy entry and exit for pigs and farm staff Huts should be positioned to provide shelter from prevailing winds and direct sun. In hot climates, huts should be placed in shaded areas or equipped with reflective roofing materials. ### Fixed Shelters and Barns Fixed shelters or barns may be used in free range systems, particularly for farrowing or weaning. These structures provide more permanent protection but require careful management to prevent disease buildup. Design considerations include: - Orientation: Buildings should be oriented to maximize natural ventilation and minimize heat gain - Flooring: Slatted or solid floors with drainage to prevent mud and manure accumulation - Bedding: Straw or other bedding materials should be provided for comfort and warmth - Lighting: Natural lighting through windows or skylights supports pig welfare and staff working conditions - Access: Multiple doors or openings allow pigs to move freely between indoor and outdoor areas Fixed shelters require regular cleaning and disinfection between groups to prevent disease transmission. ### Wallows and Shade Wallows are essential for thermoregulation in free range pigs, particularly in hot climates. Pigs lack functional sweat glands and rely on wallowing to cool themselves. Design considerations include: - Location: Wallows should be placed in shaded areas away from feed and water sources - Size: Wallows should be large enough for multiple pigs to use simultaneously - Depth: Wallows should be 15 to 30 centimeters deep with gradual slopes for easy entry and exit - Water source: Clean water should be available for filling and maintaining wallows - Drainage: Wallows should drain away from housing and feeding areas to prevent mud accumulation Shade can be provided by trees, shade cloth, or roofed structures. Pigs require access to shade during hot weather to prevent heat stress. ### Fencing and Containment Perimeter fencing is essential for containing pigs and excluding predators and wildlife. Fencing design depends on pig size, predator pressure, and regulatory requirements. Common fencing options include: - Electric fencing: Temporary or permanent electric fencing can contain pigs and deter predators - Mesh fencing: Welded wire or woven mesh fencing provides physical containment - Barbed wire: Barbed wire may be used for perimeter fencing but requires careful management to prevent injury - Hedge rows: Natural barriers such as hedges or ditches can supplement fencing Fencing should be regularly inspected and maintained to prevent escapes and predator entry. ## Welfare Outcomes and Health Management Free range pig farming can provide welfare benefits through increased space, environmental enrichment, and natural behaviors. However, free-range systems also present specific health and welfare challenges that require active management. ### Welfare Benefits Free range systems allow pigs to express natural behaviors including rooting, foraging, social interaction, and exploration. These behaviors are associated with reduced stress and improved welfare outcomes. Pigs in free-range systems typically have lower rates of stereotypic behaviors such as bar biting and sham chewing compared to confined systems. ### Health Challenges Free range pig farming is associated with specific health challenges that differ from confined systems. These include: - Parasite exposure: Free-range pigs have higher exposure to internal and external parasites due to contact with soil and wildlife. A 2022 study on the prevalence of swine gastrointestinal parasites in two free-range farms from Nord-West Region of Romania documented parasite burdens in free-range systems (PubMed, Pathogens, 2022). - Disease transmission: Contact with wildlife and other livestock increases the risk of disease introduction. A 2023 study on seroconversion of a swine herd in a free-range rural multi-species farm against HPAI H5N1 2.3.4.4b clade virus documented influenza transmission in multi-species free-range settings (PubMed, Microorganisms, 2023). - Lameness and osteochondrosis: A 2015 study on osteochondrosis, but not lameness, is more frequent among free-range pigs than confined herd-mates found that free-range pigs had higher rates of osteochondrosis lesions (Elsevier, Acta Veterinaria Scandinavica, 2015). - Influenza virus evolution: A 2022 study on evolution of influenza A virus in intensive and free-range swine farms in Spain documented viral circulation patterns in free-range systems (PubMed, Virus Evolution, 2022). ### Parasite Control Parasite control in free range pig farming requires an integrated approach including: - Pasture rotation: Moving pigs to fresh pasture breaks parasite life cycles and reduces exposure - Fecal monitoring: Regular fecal sampling and testing for parasite eggs guides treatment decisions - Targeted deworming: Treating only affected animals reduces selection for resistance - Pasture management: Harrowing or resting pastures reduces parasite survival - Wildlife exclusion: Fencing and habitat management reduces wildlife contact Farmers should work with a veterinarian to develop a parasite control program specific to their farm conditions. ### Lameness Management Lameness in free range pigs can result from trauma, infection, or developmental conditions. Management strategies include: - Regular lameness scoring: Walking all pigs regularly and scoring gait abnormalities - Prompt treatment: Isolating and treating lame pigs to prevent worsening - Pasture management: Maintaining even ground surfaces and avoiding muddy areas - Nutrition: Ensuring adequate mineral and vitamin intake for bone and joint health - Genetic selection: Selecting breeding stock with sound conformation Farmers should consult a veterinarian for persistent or severe lameness cases. ## Biosecurity and Disease Prevention Biosecurity is critical in free range pig farming due to increased exposure to disease vectors. Effective biosecurity programs reduce the risk of disease introduction and spread. ### Perimeter Biosecurity Perimeter biosecurity measures for free range pig farms include: - Perimeter fencing: Secure fencing to exclude wildlife and prevent pig escapes - Entry controls: Locked gates, signage, and visitor protocols - Vehicle disinfection: Wheel washes or spray stations for vehicles entering the farm - Wildlife management: Habitat modification and exclusion to reduce wildlife contact - Dead stock disposal: Proper disposal of mortalities to prevent scavenger attraction ### Internal Biosecurity Internal biosecurity measures reduce disease spread within the farm: - Quarantine: Isolating new or returning pigs for observation and testing - All-in/all-out management: Moving groups of pigs together to prevent mixing - Equipment sanitation: Cleaning and disinfecting equipment between groups - Staff hygiene: Boot washes, hand washing, and dedicated clothing for different areas - Feed storage: Secure feed storage to prevent wildlife and pest access ### Disease Surveillance Disease surveillance in free range pig farming should include: - Daily health checks: Observing all pigs for signs of illness - Mortality monitoring: Recording and investigating all deaths - Diagnostic testing: Regular testing for endemic and emerging diseases - Reporting: Notifying veterinary authorities of suspect notifiable diseases A 2021 study on from national biosecurity measures to territorial ASF preparedness: the case of free-range pig farming in Corsica, France documented biosecurity challenges specific to free-range systems (PubMed, Frontiers in [Veterinary Science](/blog/news/veterinary-science), 2021). The USDA Animal and Plant Health Inspection Service provides resources on swine disease management relevant to free-range operations (USDA APHIS, www.aphis.usda.gov/livestock-poultry-disease/swine). ## Pasture Management and Rotation Pasture management is essential for maintaining soil health, reducing parasite burdens, and providing adequate nutrition for free range pigs. ### Stocking Density Stocking density affects pasture health, pig welfare, and disease risk. Factors influencing appropriate stocking density include: - Soil type: Sandy soils drain well but may erode, clay soils hold moisture but become muddy - Climate: Wet climates require lower stocking densities to prevent mud and manure accumulation - Pasture type: Different grass and legume species have varying carrying capacities - Season: Pasture growth rates vary by season, affecting carrying capacity - Pig class: Sows with litters require more space than weaners or growers Farmers should monitor pasture condition and adjust stocking density as needed. ### Pasture Rotation Pasture rotation involves moving pigs to fresh pasture on a regular schedule. Benefits include: - Parasite control: Breaking parasite life cycles by moving pigs before reinfection - Soil health: Allowing pasture to recover between grazing periods - Nutrient distribution: Spreading manure evenly across the farm - Weed control: Preventing overgrazing and weed establishment Rotation schedules depend on pasture growth rates, pig density, and parasite pressure. Typical rotation intervals range from 7 to 21 days. ### Pasture Renovation Pasture renovation may be necessary to maintain productivity and health. Renovation practices include: - Reseeding: Planting new grass or legume species to improve pasture quality - Harrowing: Breaking up manure pats and aerating soil - Rolling: Firming soil and leveling ground surfaces - Fertilizing: Applying appropriate fertilizers based on soil testing - Resting: Allowing pasture to recover for extended periods ## Records and Measurements Accurate records are essential for managing free range pig farming operations and meeting certification requirements. ### Required Records Certification programs and regulatory authorities typically require records of: - Stock numbers: Pig inventory by age, sex, and production stage - Movements: Pig arrivals, departures, and transfers between groups - Health treatments: Medications, vaccines, and veterinary visits - Mortality: Deaths, causes, and disposal methods - Feed: Feed types, amounts, and sources - Pasture: Rotation schedules, stocking densities, and pasture condition - Water: Water sources, testing results, and treatment ### Monitoring Parameters Key monitoring parameters for free range pig farming include: - [Body condition scoring](/knowledge/animal-farming/farm-management/body-condition-scoring-a-tool-for-feed-management): Regular assessment of pig body condition - Lameness scoring: Gait assessment using standardized scoring systems - Parasite burdens: Fecal egg counts and clinical signs - Pasture condition: Visual assessment of pasture cover and soil health - Water quality: Testing for contaminants and pathogens - Mortality rates: Tracking deaths by cause and production stage ### Record Keeping Systems Record keeping systems can be paper-based or electronic. Effective systems should be: - Simple: Easy to use and understand for all farm staff - Consistent: Standardized formats and definitions - Accessible: Available for review by farm staff and auditors - Secure: Protected from loss or damage - Compliant: Meeting regulatory and certification requirements ## Common Failure Patterns Free range pig farming systems can fail due to several common patterns that farmers should recognize and address. ### Pasture Degradation Pasture degradation occurs when stocking density exceeds carrying capacity or rotation intervals are too long. Signs include: - Bare soil patches - Mud accumulation - Weed invasion - Erosion - Reduced pasture growth Prevention requires appropriate stocking density, regular rotation, and pasture renovation as needed. ### Parasite Overload Parasite overload occurs when parasite control measures are inadequate. Signs include: - Poor growth rates - Diarrhea - Anemia - Rough hair coats - Reduced feed efficiency Prevention requires integrated parasite control including pasture rotation, fecal monitoring, and targeted treatment. ### Disease Outbreaks Disease outbreaks in free range systems can result from wildlife contact, contaminated feed, or inadequate biosecurity. A 2022 study on the impact of the epidemic experience on the recovery of production of pig farmers after the outbreak: evidence from the impact of [African swine fever](/knowledge/bioinformatics/african-swine-fever-computational-models-for-early-detection-and-spread-prediction-in-wild-boar-populations) (ASF) in Chinese pig farming documented recovery challenges after disease outbreaks (PubMed, Preventive [Veterinary Medicine](/blog/careers/veterinary-medicine-careers-from-clinical-practice-to-public-health), 2022). A 2022 study on the prevention and control of African swine fever among rural free-range farmers in China examined biosecurity gaps in free-range settings (Elsevier, Journal of Catastrophology, 2022). ### Predator Losses Predator losses can be significant in free range systems, particularly for young pigs. Common predators include: - Foxes - Coyotes - Dogs - Birds of prey - Bears Prevention requires secure fencing, guardian animals, and predator management programs. ### Weather Extremes Weather extremes can cause welfare problems and mortality in free range pigs. Common issues include: - Heat stress: Lack of shade or wallows during hot weather - Cold stress: Inadequate shelter or bedding during cold weather - Mud: Excessive rainfall causing muddy conditions - Flooding: Low-lying pastures becoming flooded Prevention requires appropriate housing, shelter, and site selection. ## [Food Safety](/knowledge/bacteria/livestock-bacteria/cooking-chicken-bacteria-prevention) Considerations Free range pig farming presents specific food safety considerations that farmers must address to meet regulatory requirements and consumer expectations. ### Pathogen Exposure Free-range pigs may have higher exposure to foodborne pathogens through contact with soil, wildlife, and environmental contamination. A study on seroprevalence of hepatitis E virus in pigs from different farming systems in the Netherlands examined pathogen prevalence across production systems (Elsevier, Journal of Food Protection, 2014). Farmers should implement measures to reduce pathogen exposure including: - Clean water sources: Protecting water supplies from fecal contamination - Feed storage: Preventing wildlife and pest access to feed - Pasture management: Avoiding contamination from wildlife feces - Pre-slaughter management: Reducing stress and contamination risk before transport ### Withdrawal Periods All medications used in free range pig farming must comply with label withdrawal periods. Farmers must maintain accurate treatment records to ensure treated animals do not enter the food chain before withdrawal periods expire. Certification programs may have additional requirements for medication use and record keeping. ### Slaughter and Processing Free-range pigs may require specific handling at slaughter to maintain welfare standards and meat quality. Farmers should communicate with processors about the origin and management of free-range pigs to ensure appropriate handling protocols. ## Professional Escalation Criteria Farmers should seek professional veterinary advice when specific conditions are observed. ### Veterinary Consultation Consult a veterinarian for: - Unexplained mortality: Deaths without obvious cause - Disease outbreaks: Multiple animals showing similar clinical signs - Notifiable disease suspicion: Signs of diseases reportable to authorities - Treatment failure: Lack of response to standard treatments - Diagnostic testing: Need for laboratory confirmation of disease The Merck Veterinary Manual provides management and nutrition guidance relevant to free-range pig operations (Merck Veterinary Manual, www.merckvetmanual.com/management-and-nutrition). ### Specialist Referral Refer to specialists for: - Complex disease investigations: Cases requiring advanced diagnostic testing - Herd health planning: Development of comprehensive health programs - Biosecurity audits: Assessment of biosecurity measures - Regulatory compliance: Interpretation of complex regulations - Certification requirements: Guidance on meeting certification standards ### Regulatory Reporting Report to regulatory authorities for: - Notifiable diseases: Diseases required by law to be reported - Food safety issues: Contamination or residue concerns - Animal welfare concerns: Suspected welfare violations - Environmental issues: Pollution or waste management problems ## Frequently Asked Questions ### What is the minimum space requirement for free range pigs? Space requirements vary by jurisdiction and certification program. Typical minimum space allowances range from 20 to 50 pigs per hectare of pasture, with additional space required for housing, feeding, and watering areas. Farmers should verify the specific requirements of their target certification program or regulatory authority. ### How do I prevent parasite problems in free range pigs? Parasite prevention requires an integrated approach including pasture rotation, fecal monitoring, targeted deworming, and wildlife exclusion. Work with a veterinarian to develop a parasite control program specific to your farm conditions and local parasite prevalence. A 2022 study on the prevalence of swine gastrointestinal parasites in two free-range farms from Nord-West Region of Romania documented parasite burdens that can occur in free-range systems (PubMed, Pathogens, 2022). ### What housing options are available for free range pigs? Common housing options include movable huts or arks, fixed shelters or barns, and combination systems. Housing should provide protection from weather extremes, predators, and disease vectors while allowing pigs to express natural behaviors. The Merck Veterinary Manual provides management guidance relevant to housing decisions (Merck Veterinary Manual, www.merckvetmanual.com/management-and-nutrition). ### How do I manage biosecurity in a free range system? Biosecurity in free range systems requires perimeter fencing, entry controls, wildlife management, quarantine protocols, and disease surveillance. A 2021 study on from national biosecurity measures to territorial ASF preparedness: the case of free-range pig farming in Corsica, France provides insights into biosecurity challenges specific to free-range systems (PubMed, Frontiers in [Veterinary Science](/blog/news/veterinary-science), 2021). The USDA APHIS offers resources on swine disease management (USDA APHIS, www.aphis.usda.gov/livestock-poultry-disease/swine). ### What are the main welfare concerns in free range pig farming? Welfare concerns include parasite exposure, disease transmission, lameness, and weather extremes. A 2015 study on osteochondrosis, but not lameness, is more frequent among free-range pigs than confined herd-mates found higher rates of osteochondrosis in free-range pigs (Elsevier, Acta Veterinaria Scandinavica, 2015). Farmers should monitor for these conditions and implement preventive management. ### How do I transition from confined to free range pig farming? Transition requires planning for housing, fencing, pasture management, and biosecurity. Start with a small group of pigs to test your system before expanding. Consult with experienced free-range farmers and certification programs for guidance. The USDA Agricultural Research Service provides research on animal production systems (USDA ARS, www.ars.usda.gov/animal-production-and-protection). ### What records do I need to keep for free range pig farming? Required records typically include stock numbers, movements, health treatments, mortality, feed, pasture rotation, and water quality. Certification programs and regulatory authorities specify record keeping requirements. Accurate records are essential for traceability and compliance. ### How do I manage disease risks from wildlife in free range systems? Wildlife disease risks can be managed through perimeter fencing, habitat modification, wildlife exclusion, and disease surveillance. A 2023 study on seroconversion of a swine herd in a free-range rural multi-species farm against HPAI H5N1 2.3.4.4b clade virus documented influenza transmission risks in multi-species free-range settings (PubMed, Microorganisms, 2023). A 2022 study on evolution of influenza A virus in intensive and free-range swine farms in Spain documented viral circulation patterns relevant to free-range management (PubMed, Virus Evolution, 2022). ## Related Farming Guides - [Systems Biology](/blog/news/systems-biology) - [Pig Farming Breeding Farrowing Nursery Grow Finish Nutrition And Biosecurity](/knowledge/animal-farming/swine/pig-farming-breeding-farrowing-nursery-grow-finish-nutrition-and-biosecurity) - [Farrowing House Preparation And Sow Care](/knowledge/animal-farming/swine/farrowing-house-preparation-and-sow-care) - [Manure Management For Pig Farms](/knowledge/animal-farming/swine/manure-management-for-pig-farms) - [Pig Barn Ventilation And Thermal Comfort](/knowledge/animal-farming/swine/pig-barn-ventilation-and-thermal-comfort) ## Related Clinical & Scientific Guides * [Pig Enrichment Programs and Behavior Monitoring](/knowledge/animal-farming/swine/pig-enrichment-programs-and-behavior-monitoring) * [Swine Handling Facility Design for Safe Pig Movement](/knowledge/animal-farming/swine/swine-handling-facility-design-safe-pig-movement) * [Swine Feeding Management for Grow-Finish Pigs](/knowledge/animal-farming/swine/swine-feeding-management-for-grow-finish-pigs) ## References and Further Reading - [www.ars.usda.gov](https://www.ars.usda.gov/animal-production-and-protection) - [www.aphis.usda.gov](https://www.aphis.usda.gov/livestock-poultry-disease/swine) - [www.merckvetmanual.com](https://www.merckvetmanual.com/management-and-nutrition) - [Prevalence of Swine Gastrointestinal Parasites in Two Free-Range Farms from Nord-West Region of Romania.](https://pubmed.ncbi.nlm.nih.gov/36145387). Pathogens (Basel, Switzerland), 2022. - [Classical Swine Fever-An Updated Review.](https://pubmed.ncbi.nlm.nih.gov/28430168). Viruses, 2017. - [Seroconversion of a Swine Herd in a Free-Range Rural Multi-Species Farm against HPAI H5N1 2.3.4.4b Clade Virus.](https://pubmed.ncbi.nlm.nih.gov/37317136). Microorganisms, 2023. - [Evolution of influenza A virus in intensive and free-range swine farms in Spain.](https://pubmed.ncbi.nlm.nih.gov/35039784). Virus evolution, 2022. - [From National Biosecurity Measures to Territorial ASF Preparedness: The Case of Free-Range Pig Farming in Corsica, France.](https://pubmed.ncbi.nlm.nih.gov/34395574). Frontiers in veterinary science, 2021. - [The impact of the epidemic experience on the recovery of production of pig farmers after the outbreak-Evidence from the impact of African swine fever (ASF) in Chinese pig farming.](https://pubmed.ncbi.nlm.nih.gov/35008013). Preventive veterinary medicine, 2022. - [Seroprevalence of hepatitis e virus in pigs from different farming systems in the Netherlands](https://doi.org/10.4315/0362-028X.JFP-13-302). Journal of Food Protection, 2014. - [A Study on the Prevention and Control of African Swine Fever Among Rural Free - Range Farmers in China](https://doi.org/10.3969/j.issn.1000-811X.2022.03.004). Journal of Catastrophology, 2022. - [Osteochondrosis, but not lameness, is more frequent among free-range pigs than confined herd-mates](https://doi.org/10.1186/s13028-015-0154-7). Acta Veterinaria Scandinavica, 2015. > This article is educational and is not a substitute for veterinary diagnosis, treatment, public-health guidance, or regulatory reporting.