Intensive pig farming is a subset of pig farming and of Industrial animal agriculture, all of which are types of animal husbandry, in which livestock domestic pigs are raised up to slaughter weight. These operations are known as AFO or CAFO in the U.S. In this system of pig production, grower pigs are housed indoors in group-housing or straw-lined sheds, whilst pregnant sows are housed in gestation crates or pens and give birth in farrowing crates.

The use of gestation crates for pregnant sows has resulted in lower birth production costs; however, this practice has led to more significant animal cruelty. Many of the world’s largest producers of pigs (US, Canada, China, Mexico) use gestation crates but some nations and nine US states have banned and removed these crates. The European Union has banned the use of gestation crates after the 4th week of pregnancy.[1]


Intensive piggeries are generally large warehouse-like buildings or barns. Indoor pig systems allow the pigs' conditions to be monitored, ensuring minimum fatalities and increased productivity. Buildings are ventilated and their temperature regulated. Most domestic pig varieties are susceptible to sunburn and heat stress, and all pigs lack sweat glands and cannot cool themselves. Pigs have a limited tolerance to high temperatures and heat stress can lead to death. Maintaining a more specific temperature within the pig-tolerance range also maximizes growth and growth-to-feed ratio. Indoor piggeries have allowed pig farming to be undertaken in countries or areas with unsuitable climate or soil for outdoor pig raising.[2] In an intensive operation, pigs will no longer need access to a wallow (mud), which is their natural cooling mechanism. Intensive piggeries control temperature through ventilation or drip water systems.

Pigs are naturally omnivorous and are generally fed a combination of grains and protein sources (soybeans, or meat and bone meal). Larger intensive pig farms may be surrounded by farmland where feed-grain crops are grown. Consequently, piggeries are reliant on the grains industry. Pig feed may be bought packaged, in bulk or mixed on-site. The intensive piggery system, where pigs are confined in individual stalls, allows each pig to be allotted a portion of feed. The individual feeding system also facilitates individual medication of pigs through feed. This has more significance to intensive farming methods, as the proximity to other animals enables diseases to spread more rapidly. To prevent disease spreading and encourage growth, drug programs such as vitamins and antibiotics are administered preemptively.

Indoor systems allow for the easy collection of waste. In an indoor intensive pig farm, manure can be managed through a lagoon system or other waste-management system. However, waste smell remains a problem which is difficult to manage.[3] Pigs in the wild or on open farmland are naturally clean animals.

The way animals are housed in intensive systems varies. Breeding sows will spend the bulk of their time in gestation crates during pregnancy. The use of these crates may be preferred as they facilitate feed management and growth control and prevent pig aggression. Sows are moved to farrowing crates, with litter, from before farrowing until weaning, to ease management of farrowing and reduce piglet loss from sows lying on them. Dry or open time for sows can be spent in indoor pens or outdoor pens or pastures. Houses should be clean and well ventilated but draught-free.

Piglets can be subjected to castration, tail docking to prevent tail biting, teeth clipping, and earmarking and tattooing for litter identification. Treatments are usually made without any pain killers.[citation needed] Weak runts could be killed shortly after birth.[citation needed] Injections with a high availability iron solution often are given, as sow's milk is low in iron. The docking due to tail biting is a common practice in intensive rearing facilities as animals in that environment are more prone to increased levels of aggression and instability.[4]

Piglets are weaned and removed from the sows at between two and five weeks old[5] and placed in sheds, nursery barns or directly to growout barns. Grower pigs are usually housed in alternative indoor housing, such as batch pens. Group pens generally require higher stockmanship skills. Such pens will usually not contain straw or other material. Alternatively, a straw-lined shed may house a larger group in age groups. Larger swine operations use slotted floors for waste removal, and deliver bulk feed into feeders in each pen; feed is available ad libitum.

Environmental impacts


Many countries have introduced laws to regulate treatment of farmed animals.


As of 2016, The European Union legislation has required that pigs be given environmental enrichment, specifically they must have permanent access to a sufficient quantity of material to enable proper investigation and manipulation activities.[6]

Under the legislation tail docking may only be used as a last resort. The law provides that farmers must first take measures to improve the pigs’ conditions and, only where these have failed to prevent tail biting, may they tail dock.[7]

United States

Nine states have banned the use of gestation crates, with Rhode Island being the most recent as of July 2012.[8]

Discharge from CAFOs is regulated by the federal Environmental Protection Agency (EPA). In 2003, the EPA revised the Clean Water Act to include permitting requirements and effluent (discharge) limitations for CAFOs. In 2008, final AFO/CAFO regulation revised portions of it under EPA’s National Point Discharge Elimination System (NPDES) permitting program.[9]

The federal Humane Slaughter Act requires pigs to be stunned before slaughter, although compliance and enforcement is questioned. There is concern from animal liberation/welfare groups that the laws have not resulted in a prevention of animal suffering and that there are "repeated violations of the Humane Slaughter Act at dozens of slaughterhouses".[10]


Sows are often confined in gestation crates, which usually does not allow the pig to turn around or lay down comfortably. Confinement farming methods have come under increasing public scrutiny due to animal welfare and environmental concerns.

Dispute regarding farming methods

Intensive piggeries have been increasingly[when?] criticized in preference of free range systems. Such systems usually refer not to a group-pen or shedding system, but to outdoor farming systems. Those that support outdoor systems usually do so on the grounds that they are more animal friendly and allow pigs to experience natural activities (e.g., wallowing in mud, relating to young, rooting soil). Outdoor systems are usually less economically productive due to increased space requirements and higher morbidity, (though, when dealing with the killing of piglets and other groups of swine, the methods are the same.) They also have a range of environmental impacts, such as denitrification of soil[11][12] and erosion. Outdoor pig farming may also have welfare implications, for example, pigs kept outside may get sunburnt and are more susceptible to heat stress than in indoor systems, where air conditioning or similar can be used.[13][14] Outdoor pig farming may also increase the incidence of worms and parasites in pigs.[15][16] Management of these problems depends on local conditions, such as geography, climate, and the availability of skilled staff.

Transition of an indoor production system to an outdoor system may present obstacles. Some breeds of pig commonly used in intensive farming have been selectively bred to suit intensive conditions. Lean pink-pigmented pigs are unsuited for outdoor agriculture, as they suffer sunburn and heat stress.[citation needed] In certain environmental conditions – for example, a temperate climate – outdoor pig farming of these breeds is possible. However, there are many other breeds of pig suited to outdoor rearing, as they have been used in this way for centuries, such as Gloucester Old Spot and Oxford Forest. Following the UK ban of sow stalls, the British Pig Executive indicates that the pig farming industry in the UK has declined.[17] The increase in production costs[18] has led to British pig-products being more expensive than those from other countries, leading to increased imports and the need to position UK pork as a product deserving a price premium.

In 1997, Grampian Country Foods, then the UK’s largest pig producer, pointed out that pigmeat production costs in the UK were 44 p/kg higher than on the continent. Grampian stated that only 2 p/kg of this was due to the ban on stalls; the majority of the extra costs resulted from the then strength of sterling and the fact that at that time meat and bone meal had been banned in the UK but not on the continent. A study by the Meat and Livestock Commission in 1999, the year that the gestation crate ban came into force, found that moving from gestation crates, to group housing added just 1.6 pence to the cost of producing 1 kg of pigmeat. French and Dutch studies show that even in the higher welfare group housing systems – ones giving more space and straw – a kg of pigmeat costs less than 2 pence more to produce than in gestation crates.[7]

Sow breeding systems

Organized campaigns by animal activists have focused on the use of the gestation crate, such as the 'gestation crate' and farrowing crate. The gestation crate has now been banned in the UK, certain US states, and other European countries, although it remains part of pig production in much of the US and European Union.

Only the sows selected for breeding will spend time in a gestation crate. In an intensive system, the sow will be placed in a crate prior mating and will stay there for at least the start of her pregnancy, when the risk of miscarriage is higher.[citation needed] The typical length of the sow's pregnancy is 3 months, 3 weeks, and 3 days. In certain cases, sows may spend this time in the crate. However, a variety of farming systems are used and the time in the crate may vary from 4 weeks to the whole pregnancy.

There is also some criticism of 'farrowing crates'. A farrowing crate houses the sow in one section and her piglets in another. It allows the sow to lie down and roll over to feed her piglets, but keeps her piglets in a separate section. This prevents the large sow from sitting on her piglets and killing them, which is quite common where the sow is not separated from the piglets.[19] Sows are also prevented from being able to move other than between standing and lying. Some models of farrowing crates may allow more space than others, and allow greater interaction between sow and young. Well-designed farrowing pens in which the sow has ample space can be just as effective as crates in preventing piglet mortality.[7] Some crates may also be designed with cost-effectiveness or efficiency in mind and therefore be smaller.

Authoritative industry data indicate that moving from sow stalls to group housing added 2 pence to the cost of producing 1 kg. of pigmeat.[7]

Many English fattening pigs are kept in barren conditions and are routinely tail docked. Since 2003 EU legislation has required pigs to be given environmental enrichment and has banned routine tail docking. However, 80% of UK pigs are tail docked.[7]

In 2015, use of sow crates was made illegal on New Zealand pig farms.[20]

Effects on traditional rural communities

Common criticism of intensive piggeries is that they represent a corporatization of the traditional rural lifestyle. Critics feel the rise of intensive piggeries has largely replaced family farming. Between 1982 and 1987 some 21% of Iowa hog farmers went out of business.[citation needed] By 1992, another 12% had gone out of business.[citation needed] In large part, this is because intensive piggeries are more economical than outdoor systems, pen systems, or the sty. In many pork-producing countries (e.g., United States, Canada, Australia, Denmark) the use of intensive piggeries has led to market rationalization and concentration. The New York Times reported that keeping pigs and other animals in "unnaturally overcrowded" environments poses considerable health risks for workers, neighbors, and consumers.[21]

Waste management and public health concerns

Contaminants from animal wastes can enter the environment through pathways such as through leakage of poorly constructed manure lagoons or during major precipitation events resulting in either overflow of lagoons and runoff from recent applications of waste to farm fields, or atmospheric deposition followed by dry or wet fallout. Runoff can leach through permeable soils to vulnerable aquifers that tap ground water sources for human consumption. Runoff of manure can also find its way into surface water such as lakes, streams, and ponds. An example of weather induced runoff having been recently reported in the wake of Hurricane Matthew.[22]

Many contaminants are present in livestock wastes, including nutrients, pathogens, veterinary pharmaceuticals and naturally excreted hormones. Improper disposal of animal carcasses and abandoned livestock facilities can also contribute to water quality problems in surrounding areas of CAFOs.[citation needed]

Exposure to waterborne contaminants can result from both recreational use of affected surface water and from ingestion of drinking water derived from either contaminated surface water or ground water. High-Risk populations are generally the very young, the elderly, pregnant women, and immunocompromised individuals. Dermal contact may cause skin, eye, or ear infections. Drinking water exposures to pathogens could occur in vulnerable private wells.[23]

At Varkensproefcentrum Sterksel in the Netherlands, a pig farm has been created that reuses its waste streams. CO² and ammonia from the pig manure are reused to grow algae which in turn are used to feed the pigs.[24]

Another method to reduce the effect on the environment is to switch to other breeds of pig. The enviropig is a genetically modified type of pig with the capability to digest plant phosphorus more efficiently than ordinary pigs, though the enviropig program ended in 2012 and did not reach commercial distribution.

Nutrient-rich runoff from CAFO's can contribute to Algal blooms in rivers, lakes and seas. The 2009 Harmful Algal Bloom event off the coast of Brittany, France was attributed to runoff from an intensive pig farm.[25]

North Carolina

As of 2010, North Carolina housed approximately ten million hogs, most of which are located in the eastern half of the state in industrialized CAFOs or Confined Animal Feeding Operations. This was not the case twenty years ago. The initial horizontal integration and the vertical integration that arose in this industry resulted in numerous issues, including issues of environmental disparity, loss of work, pollution, animal rights, and overall general public health. The most remarkable example of swine CAFO monopoly is found in the United States, where in 2001, 50 producers had control over 70% of total pork production. In 2001, the biggest CAFO had just over 710,000 sows.[26]

Originally, Murphy Family Farms horizontally integrated the North Carolina system. They laid the groundwork for the industry to be vertically integrated. Today[when?] the hog industry in North Carolina is led by Smithfield Foods, which has expanded into both nationwide and international production.[27]

The environmental justice problems in North Carolina's agroindustrialization of swine production seem to stem from the history of the coastal region's economy, which has relied heavily on black and low-income populations to supply the necessary agricultural labor. The industry's shift from family-owned hog farms to factory hogging has contributed to the frequent targeting of these areas.[28]

This swine production and pollution that accompanies factory hogging is concentrated in the parts of North Carolina that have the highest disease rates, the least access to medical care, and the greatest need for positive education and economic development.[29] Since hog production has become consolidated in the coastal region of N.C., the high water tables and low-lying flood plains have increased the risk and impact of hog farm pollution. A swine CAFO is made up of three parts: the hog house, the “lagoon,” and the “spray field.” Waste disposal techniques used by small-scale traditional hog farms, like using waste as fertilizer for commercially viable crops, were adopted and expanded for use by CAFOs. Lagoons are supposed to be protected with an impermeable liner, but some do not work properly. This can cause environmental damage, as seen in 1995 when a lagoon burst in North Carolina. This lagoon released 25 million gallons of noxious sludge into North Carolina’s New River and killed approximately eight to ten million fish.[30]

The toxins emitted by the swine CAFOs can produce a variety of symptoms and illnesses ranging from respiratory disorders, headaches, and shortness of breath to hydrogen sulfide poisoning, bronchitis, and asthma. The potential for spray field runoff or lagoon leakage puts nearby residents in danger of contaminated drinking water, which can lead to diseases like samonellosis, giardiasis, Chlamydia, meningitis, cryptosporidiosis, worms, and influenza.[31]


Slaughterhouses and veterinarians are obliged to report pigs with injuries to the Ministry of Food, Agriculture and Fisheries, which forwards cases to the police. There were relatively few cases before 2006, but by 2008-9 there were about 300 per year.[32] When there are visible injuries, it represents not only a problem in animal welfare but also the farmers economy because parts or occasionally the entire carcass has to be discarded.[32] From 2006 to 2009 the number of pigs with injuries caused by hard objects, such as planks or chains received by slaughterhouses rose significantly. It was possibly related to a system introduced in 2006, which rewards "the rushed loading of animals onto vehicles", as well as a sharp increase in uneducated Eastern European farm workers unaware of Danish laws.[33][32]

Gestation crates were sometimes used on some Danish farms to restrict the movement of sows during pregnancy, as documented by British celebrity chef Jamie Oliver in a television programme for the UK's Channel 4 in 2009.[34] In other fields, such as bathing facilities for the pigs and floor material Danish requirements were higher than in the UK.[34] As of 2008 the practice was already prohibited for pigs exported to the UK.[35] The use of gestation crates became illegal in Denmark (as part of the EU) in 2013.[36][37][38]

New Zealand

According to Scoop, in 2009 the New Zealand pork industry was "dealt a shameful public relations slap-in-the-face after its former celebrity kingpin, Mike King, outed their farming practices as 'brutal', 'callous' and 'evil'" on a May episode of New Zealand television show Sunday. King condemned the "appalling treatment" of factory farmed pigs. King observed conditions inside a New Zealand piggery, and saw a dead female pig inside a gestation crate, lame and crippled pigs and others that could barely stand, pigs either extremely depressed or highly distressed, pigs with scars and injuries, and a lack of clean drinking water and food.

Sow crate farming should be illegal and we should outlaw it right now. It is absolutely disgusting and I am sorry that I was part of it

— Mike King, 2009[39]

See also


  1. ^ Werblow, Steve (27 January 2014). "Gestation crates: News from the front lines". Pork Network. Retrieved 3 October 2015. 
  2. ^ "Australian pork page on Pig welfare". Australainpork.com.au. Retrieved 28 July 2017. 
  3. ^ G. Galvin; K.D. Casey S.A. Lowe; N.A. Hudson; M.A. Atzeni; E.J. McGahan (12 October 2003). "Spatial Variability Of Odor Emissions From Anaerobic Piggery Lagoons In Queensland". Air Pollution from Agricultural Operations III, Proceedings of the 12–15 October 2003 Conference (Research Triangle Park, North Carolina USA). St. Joseph, MI: American Society of Agricultural and Biological Engineers. pp. 292–302. 701P1403. 
  4. ^ EFSA. Scientific Opinion of the Panel on Animal Health and Welfare (Question No EFSA-Q-2006-013) Adopted on 6 December 2007 The risks associated with tail biting in pigs and possible means to reduce the need for tail docking considering the different housing and husbandry systems Efsa.europa.eu
  5. ^ "Revisiting Weaning Age Trends, Dynamics". Nationalhogfarmer.com. 15 October 2005. Retrieved 28 July 2017. 
  6. ^ "COMMISSION RECOMMENDATION (EU) 2016/336". http://eur-lex.europa.eu. Retrieved 11 October 2017.  External link in website= (help)
  7. ^ a b c d e "Species: pigs - Compassion in World Farming". Ciwf.org.uk. Retrieved 28 July 2017. 
  8. ^ Marcelo, Philip. New R.I. law bans cutting dairy-cow tails, raising pigs and calves in crates Providence Journal, June 21, 2012. Accessed July 31, 2012.
  9. ^ "Archived copy" (PDF). Archived from the original (PDF) on 2009-05-09. Retrieved 2011-04-09. 
  10. ^ "Animal Welfare Institute Quarterly – Humane Slaughter Act Resolution Introduced". Awionline.org. Archived from the original on 3 March 2016. Retrieved 28 July 2017. 
  11. ^ "The fate of nitrogen in outdoor pig production" (PDF). Edpsciences.org. Retrieved 28 July 2017. 
  12. ^ "Archived copy" (PDF). Archived from the original (PDF) on 2008-06-25. Retrieved 2008-12-04. 
  13. ^ "Managing Heat Stress in Outdoor pigs". Depts.ttu.edu. Retrieved 28 July 2017. 
  14. ^ "Heat stress index chart for swine producers". Thepigsite.com. Retrieved 28 July 2017. 
  15. ^ Roepstorff A, Murrell KD (May 1997). "Transmission dynamics of helminth parasites of pigs on continuous pasture: Ascaris suum and Trichuris suis". Int. J. Parasitol. 27 (5): 563–72. doi:10.1016/S0020-7519(97)00022-2. PMID 9193950. 
  16. ^ "Management Control and Prevention - Managing Pig Health and Treating Pig Dieases on ThePigSite.com". The Pig Site. Retrieved 28 July 2017. 
  17. ^ "British Pig Executive market update September 2005" (PDF). Bpex.org. Retrieved 28 July 2017. 
  18. ^ "Another Move Away from Pork Crates," Farm Futures, May 8, 2012.
  19. ^ “Piglet Losses,” University of Illinois Extension, November 5, 2003.
  20. ^ "Sow crates to be phased out by 2015". The New Zealand Herald. 1 December 2010. Retrieved 4 October 2011. 
  21. ^ Kakutani, Michiko (20 November 2009). "'You Know That Chicken Is Chicken, Right?'". The New York Times. Retrieved 28 July 2017 – via NYTimes.com. 
  22. ^ Fritz, Arelis R. Hernández, Angela; Mooney, Chris; Fritz, Arelis R. Hernández, Angela; Mooney, Chris (16 October 2016). "Factory farming practices are under scrutiny again in N.C. after disastrous hurricane floods". The Washington Post. Retrieved 28 July 2017. 
  23. ^ Burkholder JoAnn; Bob Libra, Peter Weyer, Susan Heathcote, Dana Kolpin, Peter S. Thorne, Michael Wichman Impacts of Waste from Concentrated Animal Feeding Operations on Water Quality. Environ Health Perspectives. (2007) 115:308–312.
  24. ^ "442 -". Innovatienetwek.onlinetouch.nl. Retrieved 28 July 2017. 
  25. ^ Chrisafis, Angelique. "Lethal algae take over beaches in northern France". The Guardian. Retrieved October 10, 2013. 
  26. ^ "Swine production: a global perspective". En.engormix.com. Retrieved 28 July 2017. 
  27. ^ Ladd, Anthony; Edwards, Bob (2002). "Corporate Swine, Capitalist Pigs: A Decade of Environmental Injustice in North Carolina". Social Justice. 29 (3): 26–46. 
  28. ^ Wimberley, Ronald C., Morris, Libbly V. (1997). The Southern Black Belt : A National Perspective. Lexington: University of Kentucky. 
  29. ^ Raine J. Environmental Justice Issues of the North Carolina Swine Industry [Masters thesis]. Durham, NC:Duke University, Nicholas School of the Environment, 1998.
  30. ^ Orlando, Laura. McFarms Go Wild, Dollars and Sense, July/August 1998, cited in Scully, Matthew. Dominion, St. Martin's Griffin, p. 257.
  31. ^ Donham K. (1998). "The impact of industrial swine production on human health". In Thu K, Durrenberger E. Pigs, Profits, and Rural Communities. Albany, NY: State University of New York Press. pp. 73–83. 
  32. ^ a b c Andreas Lindquist (26 July 2010). Danske svin bliver banket gule og blå. Politiken. Retrieved 31 May 2016
  33. ^ "Alleged Increase in Pig Cruelty". The Pig Site. Retrieved 28 July 2017. 
  34. ^ a b "Response to 'Jamie Saves Our Bacon'". Archived from the original on May 4, 2009. Retrieved 2009-12-19.  . Danish Bacon and Meat Council, January 2009.
  35. ^ Christian Coff, David Barling, Michiel Korthals, Thorkild Nielsen, Ethical Traceability and Communicating Food, pp.90–91, Springer, 2008 ISBN 1-4020-8523-0.
  36. ^ Jacky Turner. Animal Breeding, Welfare and Society. Earthscan, London. ISBN 978-1844075898
  37. ^ Humane Society International/Canada. Ban Gestation Crates. Retrieved 31 May 2016
  38. ^ Anima (25 October 2012). Livet i fikseringsboksen. Retrieved 31 May 2016
  39. ^ "Mike King Condemns NZ Pig Cruelty - Scoop News". Scoop.co.nz. Retrieved 28 July 2017. 

External links

US Government regulation
Proponent, neutral, and industry-related
Criticism of intensive pig farming