Pig farming

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Large White piglets on a farm
A Large White sow suckling her piglets
Interior of pig farm at Bjärka-Säby Castle, Sweden, 1911

Pig farming is the raising and breeding of domestic pigs as livestock, and is a branch of animal husbandry. Pigs are farmed principally for food (e.g. pork, bacon, gammon) and skins.

Pigs are amenable to many different styles of farming: intensive commercial units, commercial free range enterprises, or extensive farming (being allowed to wander around a village, town or city, or tethered in a simple shelter or kept in a pen outside the owner's house). Historically, farm pigs were kept in small numbers and were closely associated with the residence of the owner, or in the same village or town.[1] They were valued as a source of meat and fat, and for their ability to convert inedible food into meat, and were often fed household food waste when kept on a homestead. Pigs have been farmed to dispose of municipal garbage on a large scale.[2]

All these forms of pig farm are in use today, though intensive farms are by far the most popular, due to their potential to raise a large amount of pigs in a very cost-efficient manner.[3] In developed nations, commercial farms house thousands of pigs in cramped, climate-controlled buildings with little to no exposure to sunlight or the outdoors.[4] Pigs are a popular form of livestock, with more than one billion pigs butchered each year worldwide, 100 million of them in the USA. The majority of pigs are used for human food but also supply skin, fat and other materials for use as clothing, ingredients for processed foods,[5] cosmetics,[6] and medical use.[7]

The activities on a pig farm depend on the husbandry style of the farmer, and range from very little intervention (as when pigs are allowed to roam villages or towns and dispose of garbage) to intensive systems where the pigs are contained in a building for the majority of their lives. Each pig farm will tend to adapt to the local conditions and food supplies and fit their practices to their specific situation.

The following factors can influence the type of pig farms in any given region:

  • Available food supply suitable for pigs
  • The ability to deal with manure or other outputs from the pig operation
  • Local beliefs or traditions, including religion
  • The breed or type of pig available to the farm
  • Local diseases or conditions that affect pig growth or fecundity
  • Local requirements, including government zoning and/or land use laws
  • Local and global market conditions and demand

Use as food[edit]

Almost all of the pig can be used as food. Preparations of pig parts into specialties include: sausage (and casings made from the intestines), bacon, gammon, ham, skin into pork scratchings, feet into trotters, head into a meat jelly called head cheese (brawn), and consumption of the liver, chitterlings, and blood (blood pudding or black pudding).

Production and trade[edit]

Global pig stocks
in 2014
 People's Republic of China 474.1
 United States 67.7
 Brazil 37.9
 Germany 28.3
 Denmark 28.1
 Vietnam 26.8
 Spain 26.6
 Russia 19.1
 Mexico 16.1
 Myanmar 13.9
World total 986.6
Source: UN
Food & Agriculture Organization

Pigs are farmed in many countries, though the main consuming countries are in Asia, meaning there is a significant international and even intercontinental trade in live and slaughtered pigs. Despite having the world's largest herd, China is a net importer of pigs, and has been increasing its imports during its economic development. The largest exporters of pigs are the United States, the European Union, and Canada. As an example, more than half of Canadian production (22.8 million pigs) in 2008 was exported, going to 143 countries.[8] Older pigs will consume eleven to nineteen litres (three to five US gallons) of water per day.[9]

Prevalence of intensive farms[edit]

In the UK there are around 11,000 pig farms. Approximately 1,400 of these units house more than 1,000 pigs and contain about 85% of the total UK pig population.[10][11] There are no legal definitions for free-range pigs, so retailers can label pork products as free-range without having to adhere to any standards or guidelines.[12] Only 3% of UK pigs spend their entire lives outdoors.[13] Because of this, the vast majority of the pork products sold in the UK come from intensive farms.[14]

There were around 50,000 pig farms in Australia in the 1960s.[15] Today, there are less than 1,400, and yet the total number of pigs bred and slaughtered for food has increased.[16] As of 2015, 49 farms housed 60% of the country's total pig population.[17][18]

Relationship between handlers and pigs[edit]

The way in which a stockperson interacts with pigs affects animal welfare which in some circumstances can correlate with production measures. Many routine interactions can cause fear, which can result in stress and decreased production.

There are various methods of handling pigs which can be separated into those which lead to positive or negative reactions by the animals. These reactions are based on how the pigs interpret a handler's behavior.

Negative interactions[edit]

Many negative interactions with pigs arise from stock-people dealing with large numbers of pigs. Because of this, many handlers can become complacent about animal welfare and fail to ensure positive interactions with pigs. Negative interactions include overly heavy tactile interactions (slaps, punches, kicks, and bites), the use of electric goads and fast movements. It can also include killing them. However, it is not a commonly held view that death is a negative interaction. These interactions can result in fear in the animals, which can develop into stress. Overly heavy tactile interactions can cause increased basal cortisol levels (a "stress" hormone).[19] Negative interactions that cause fear mean the escape reactions of the pigs can be extremely vigorous, thereby risking injury to both stock and handlers. Stress can result in immunosuppression,[20] leading to an increased susceptibility to disease. Studies have shown that these negative handling techniques result in an overall reduction in growth rates of pigs.

Positive interactions[edit]

Various interactions can be considered either positive or neutral. Neutral interactions are considered positive because, in conjunction with positive interactions, they contribute to an overall non-negative relationship between a stock-person and the stock. Pigs are often fearful of fast movements. When entering a pen, it is good practice for a stock-person to enter with slow and deliberate movements. These minimize fear and therefore reduce stress. Pigs are very curious animals. Allowing the pigs to approach and smell whilst patting or resting a hand on the pig's back are examples of positive behavior. Pigs also respond positively to verbal interaction. Minimizing fear of humans allow handlers to perform husbandry practices in a safer and more efficient manner. By reducing stress, stock are made more comfortable to feed when near handlers, resulting in increased productivity.[21] In other words, pigs are very social and intelligent animals, and if they are treated well, better meat can be obtained. Prohand for pigs is a training program that teaches handlers to interact with pigs in a way that promotes safe handling. It promotes the development of positive behaviors and elimination of negative behaviors. This program has been seen to improve productivity without any capital investment.[22]

Impacts on sow breeding[edit]

A sow that is suffering from a birth-induced prolapse.

Hogs raised in confinement systems tend to produce 23.5 piglets per year. From 2013 to 2016, sow death rates have nearly doubled from 5.8%-10.2%, 25-50% of these deaths have been caused by prolapse.[23]

Other probable causes of death include vitamin deficiency, mycotoxins in feed, high density diets or abdominal issues.[24] Currently mortality data is being collected by Iowa's Pork Industry Center in collaboration with the National Pork Board to collect data from over 400,000 sows from 16 U.S. states. The farms all range in different size and facility types. Raising rates in death are a profit concern to the industry, so money is being invested into research to find potential solutions of preventing prolapse.[25]

Genetic manipulation[edit]

Pigs were originally bred to rapidly gain weight and backfat in the late 1980s. In a more fat-conscious modern day America, pigs are now being bred to have less back fat and produce more offspring, which pushes the sow's body too far and is deemed one of the causes of the current prolapse epidemic. Researchers and veterinarians are seeking ways to positively impact the health of the hogs and benefit the hog business without taking much from the economy.[26]

Pig slaughter[edit]

Undercover slaughter footage.

While capable of living 10-12 years, most pigs are slaughtered when they are 5-6 months old.[27][28] Transportation from the piggery to the slaughterhouse often involves cramped conditions and long distances traveled without food, water or protection from extreme heat or cold.[29][30] At the slaughterhouse, the pigs will wait in small concrete or metal holding pens, typically overnight, still without food to minimize fecal contamination and with limited or no access to water. Eventually, they are forcefully herded to the kill floor, often with an electric prodder.[31] The most common method of stunning and killing pigs is the carbon dioxide gas chamber, which is used at all major pig abattoirs and touted as the most humane and efficient option.[32] Around one third of pigs in the UK are killed in gas chambers.[33] A system of rotating cages lowers the fully conscious pigs two or three at a time into the highly concentrated gas, which burns their eyes, nostrils, sinuses, throat, and lungs while suffocating them to death.[34][35] Because of the large size of sows, the gas is less effective on them, and they are sent into the chamber gondolas one at a time. Once tipped out the other side of the chamber, the pigs’ throats are cut, and they are bled out. However, some still emerge partly conscious, in which case they may also be electrically stunned prior to being bled out.[36]

Electrical stunning, which is the only method used used at smaller slaughterhouses, has a much higher chance of failure. Incorrect amperage, positioning of the stunner, or length of time applied can lead to the pig regaining consciousness or even being paralyzed and unable to move while still capable of feeling pain while bleeding out.[37][38] Stunning is often poorly executed by rushed slaughterhouse workers, which results in an estimated 1.8 million pigs a year in the UK regaining consciousness on the production line each year and being fully conscious as they die from blood loss, and 244,800 pigs a year are incorrectly stunned and do not lose consciousness at all.[39][40]

Captive-bolt pistols are another option used by smaller slaughterhouses. The penetrative variety fire a rod through the skull of the animal to permanently damage their brain, preventing them from regaining consciousness, while non-penetrative bolt pistols deliver blunt force trauma much like a hammer. Effective stunning requires the gun to be angled and positioned at the correct part of the head, which is often difficult if the head is not restrained.[41] Pigs are relatively intelligent and are generally reluctant to enter the bolt gun knockbox, due to having witnessed or heard other pigs being killed before them or being able to smell the blood on the floor. The bolt gun is even less effective on larger pigs, like sows. For them, a rifle may be used as an alternative, but in this case, accuracy is even more difficult.[42] Some slaughterhouses will just use a sledgehammer.[43][44] After they have been bled out, pigs are typically dropped into tanks of scalding water in order to soften their skin and remove bristles and hair. Those who have not been stunned and killed properly finally die by drowning.[45]


Pigs are extensively farmed, and therefore the terminology is well developed:

  • Pig, hog, or swine, the species as a whole, or any member of it. The singular of "swine" is the same as the plural.
  • Shoat, piglet, or (where the species is called "hog") pig, unweaned young pig, or any immature pig[46]
  • Sucker, a pig between birth and weaning
  • Weaner, a young pig recently separated from the sow
  • Runt, an unusually small and weak piglet, often one in a litter
  • Boar or hog, male pig of breeding age
  • Barrow, male pig castrated before puberty
  • Stag, male pig castrated later in life (an older boar after castration)
  • Gilt, young female not yet mated, or not yet farrowed, or after only one litter (depending on local usage).[47]
  • Sow, breeding female, or female after first or second litter

Pigs for slaughter[edit]

Finishing pigs on a farm
  • Suckling pig, a piglet slaughtered for its tender meat
  • Feeder pig, a weaned gilt or barrow weighing between 18 kg (40 lb) and 37 kg (82 lb) at 6 to 8 weeks of age that is sold to be finished for slaughter
  • Porker, market pig between 30 kg (66 lb) and about 54 kg (119 lb) dressed weight
  • Baconer, a market pig between 65 kg (143 lb) and 80 kg (180 lb) dressed weight. The maximum weight can vary between processors.
  • Grower, a pig between weaning and sale or transfer to the breeding herd, sold for slaughter or killed for rations.[clarification needed]
  • Finisher, a grower pig over 70 kg (150 lb) liveweight
  • Butcher hog, a pig of approximately 100 kg (220 lb), ready for the market. In some markets (Italy) the final weight of butcher pig is in the 180 kg (400 lb) range. They tend to have hind legs suitable to produce cured ham
  • Backfatter, cull breeding pig sold for meat; usually refers specifically to a cull sow, but is sometimes used in reference to boars


  • Herd, a group of pigs, or all the pigs on a farm or in a region
  • Sounder, a small group of pigs (or wild boar) foraging in woodland

Pig parts[edit]

  • Trotters, the hooves of pigs (they have four hoofed toes on each foot, walking mainly on the larger central two)


  • In pig, pregnant
  • Farrowing, giving birth
  • Hogging, a sow when on heat (during estrus)


  • Sty, a small pig-house, usually with an outdoor run or a pig confinement
  • Pig-shed, a larger pig-house
  • Ark, a low semi circular field-shelter for pigs
  • Curtain-barn, a long, open building with curtains on the long sides of the barn. This increases ventilation on hot, humid summer days

Environmental and health impacts[edit]

A typical man-made lagoon filled with the pig feces, urine, and blood from the adjacent intensive pig farm.

Feces and waste often spread to surrounding neighborhoods, polluting air and water with toxic waste particles.[48] Waste from swine on these farms carry a host of pathogens and bacteria as well as heavy metals. These toxins can leach down through the soil into groundwater, polluting local drinking water supplies. Pathogens can also become airborne, polluting the air and harming individuals when ingested.[49] Contents from waste have been shown to cause many detrimental health implications, as well as harmful algal blooms in surrounding bodies of water.[50]


Growth Promoters[edit]


Most pigs in America get ractopamine to put on more muscle instead of fat, to put on weight more quickly, to reduce costs and to reduce pollutants in the environment because pigs on ractopamine do not need as much feed to reach finishing weight and do not produce as much manure. However, ractopamine has not been approved for use by the European Union, China, Russia, and several other countries.[51]


China once used colistin (an antibiotic) as growth promoter (subtherapeutic antibiotic use) but discovered a colistin-resistant form of E. coli bacteria in a pig from a Shanghai farm in 2013. Investigations then led to the identification of "a gene called MCR-1 that allowed bacteria to survive colistin treatment in animals and humans."[52] In 2016, these findings led China to ban colistin as growth promoter.[52][53]


China uses sulfamethazine, bacitracin, chlortetracycline, tetracycline, florfenicol, sulfonamide, doxycycline, oxytetracycline, fluoroquinolone, macrolide, and trimethoprim,[citation needed] and stopped using colistin as of 26 July 2016.[52][53]

See also[edit]


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  17. ^ AgriFutures, Australia http://www.agrifutures.com.au/farm-diversity/pigs-for-meat-pork/. Missing or empty |title= (help)
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