HOME

TheInfoList




The pig (''Sus domesticus''), often called swine, hog, or domestic pig when distinguishing from other members of the genus '' Sus'', is an
omnivorous An omnivore () is an animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular ...
,
domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another group to secure a more predictable supply of resources from that sec ...
even-toed hoofed mammal. It is variously considered a
subspecies In biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactio ...
of the
Eurasian boar
Eurasian boar
or a distinct
species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

species
, but the
American Society of Mammalogists The American Society of Mammalogists (ASM) was founded in 1919. Its primary purpose is to encourage the study of mammal Mammals (from Latin language, Latin , 'breast') are a group of vertebrate animals constituting the class (biology), clas ...
considers it the latter. The pig's head-plus-body length ranges from , and adult pigs typically weigh between , with well-fed individuals even exceeding this range. The size and weight of hogs largely depends on their breed. Compared to other
artiodactyl The even-toed ungulates (Artiodactyla , ) are ungulate Ungulates ( ) are members of the diverse clade A clade (; from grc, , ''klados'', "branch"), also known as a monophyletic group or natural group, is a group of organisms that are mo ...
s, a pig's head is relatively long and pointed. Most even-toed ungulates are
herbivorous A herbivore is an animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular r ...
, but pigs are omnivores, like their wild relative. Pigs grunt and make snorting sounds. When used as
livestock Livestock are the domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another group to secure a more predictabl ...
, pigs are
farmed Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentary Image:Family watching television 1958.jpg, Exercise trends, Increases in sedentary behaviors su ...
primarily for the production of meat, called
pork Pork is the culinary name for the meat of the Pig, domestic pig (''Sus scrofa domesticus''). It is the most commonly consumed meat worldwide, with evidence of pig animal husbandry, husbandry dating back to 5000 BC. Pork is eaten both freshly ...

pork
. A group of pigs is called a passel, a team, or a sounder. The animal's bones, hide, and bristles are also used in products. Pigs, especially miniature breeds, are kept as pets.


Biology

The pig typically has a large head, with a long snout which is strengthened by a special prenasal bone and a disk of
cartilage Cartilage (cartilaginous tissue) is a resilient and smooth elastic tissue Elastic fibers (or yellow fibers) are an essential component of the extracellular matrix In biology Biology is the natural science that studies life and living org ...

cartilage
at the tip. The snout is used to dig into the soil to find food and is a very acute sense organ. The
dental formula Dentition pertains to the development of teeth and their arrangement in the mouth In animal anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biolo ...
of adult pigs is , giving a total of 44
teeth A tooth (plural teeth) is a hard, calcified Calcification is the accumulation of calcium salts in a Tissue (biology), body tissue. It normally occurs in the formation of bone, but calcium can be deposited abnormally in soft tissue,Miller, J. ...

teeth
. The rear teeth are adapted for crushing. In the male, the canine teeth can form
tusk Tusks are elongated, continuously growing front teeth A tooth (plural teeth) is a hard, calcification, calcified structure found in the jaws (or mouths) of many vertebrates and used to Mastication, break down food. Some animals, particularly c ...

tusk
s, which grow continuously and are sharpened by constantly being ground against each other. Four
hoof A hoof ( or ), plural hooves ( or ) or hoofs , is the tip of a toe Toes are the digits (fingers) of the foot of a tetrapod. Animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology) ...
ed toes are on each foot, with the two larger central toes bearing most of the weight, but the outer two also being used in soft ground. Most pigs have rather a
bristle 270px, The bristles of a sweeping brush A bristle is a stiff hair Hair is a protein filament In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry ...
d sparse hair covering on their skin, although
wool Wool is the textile A textile is a flexible material made by creating an interlocking bundle of yarn Yarn is a long continuous length of interlocked fibres, suitable for use in the production of textiles, sewing, crocheting, knitti ...
ly-coated breeds such as the
Mangalitsa , about one month old, in Münsterland, Germany File:Hungarian Mangalica Pig.jpg, The curly blonde coat of a Mangalica pig at HungarianHungarian may refer to: * Hungary, a country in Central Europe * Kingdom of Hungary, state of Hungary, exi ...

Mangalitsa
exist. Pigs possess both
apocrine Apocrine () is a term used to classify exocrine glands Exocrine glands are gland A gland is a group of cells in an animal's body that synthesizes substances (such as hormone A hormone (from the Greek participle , "setting in motion") is an ...
and
eccrine sweat gland Eccrine sweat glands (; from ''ekkrinein'' " secrete"; sometimes called merocrine Merocrine (or eccrine) is a term used to classify exocrine gland Exocrine glands are glands that secrete substances onto an Epithelium, epithelial surface by way ...
s, although the latter appear limited to the snout and dorsonasal areas. Pigs, however, like other "hairless" mammals (e.g. elephants, rhinos, and mole-rats), do not use thermal sweat glands in cooling. Pigs are also less able than many other mammals to dissipate heat from wet
mucous membrane A mucous membrane or mucosa is a biological membrane, membrane that lines various cavities in the body and covers the surface of internal organs. It consists of one or more layers of Epithelium, epithelial cells overlying a layer of loose connecti ...
s in the mouth through panting. Their thermoneutral zone is . At higher temperatures, pigs lose heat by wallowing in mud or water via evaporative cooling, although it has been suggested that wallowing may serve other functions, such as protection from sunburn, control, and scent-marking. Pigs are one of four known mammalian species which possess mutations in the
nicotinic acetylcholine receptor Image:Nicotine-2D-skeletal.png, Nicotine Nicotinic acetylcholine receptors, or nAChRs, are Receptor (biochemistry), receptor polypeptides that respond to the neurotransmitter acetylcholine. Nicotinic receptors also respond to drugs such as the ...
that protect against snake venom.
Mongoose A mongoose is a small terrestrial carnivorous A carnivore , meaning "meat Meat is animal flesh that is eaten as food. Humans have hunted and killed animals for meat since prehistoric times. The advent of civilization allowed the domes ...

Mongoose
s,
honey badger The honey badger (''Mellivora capensis''), also known as the ratel ( or ), is a mammal widely distributed in Africa, Southwest Asia, and the Indian subcontinent. Because of its wide range and occurrence in a variety of habitats, it is listed as ...

honey badger
s,
hedgehog A hedgehog is a spiny mammal of the subfamily Erinaceinae, in the eulipotyphlan family (biology), family Erinaceidae. There are seventeen species of hedgehog in five genus, genera found throughout parts of Europe, Asia, and Africa, and in Ne ...

hedgehog
s, and pigs all have modifications to the receptor pocket which prevents the
snake venom Snake venom is a highly toxic saliva Saliva (commonly referred to as spit) is an extracellular fluid Extracellular fluid (ECF) denotes all body fluid outside the cells of any multicellular organism. Total body water in healthy adults is abo ...
α-neurotoxin from binding. These represent four separate, independent mutations. Pigs have small lungs in relation to their body size, and are thus more susceptible than other domesticated animals to fatal
bronchitis Bronchitis is inflammation of the bronchi A bronchus is a passage or airway in the respiratory system The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structur ...

bronchitis
and
pneumonia Pneumonia is an condition of the primarily affecting the small air sacs known as . Symptoms typically include some combination of or dry , , , and . The severity of the condition is variable. Pneumonia is usually caused by with es or , a ...

pneumonia
.


Taxonomy

The pig is most often considered to be a
subspecies In biological classification In biology Biology is the natural science that studies life and living organisms, including their anatomy, physical structure, Biochemistry, chemical processes, Molecular biology, molecular interactio ...
of the
wild boar The wild boar (''Sus scrofa''), also known as the wild swine, common wild pig, Eurasian wild pig, or simply wild pig, is a suid native to much of Eurasia Eurasia () is the largest continental area on Earth, comprising all of Europe and ...

wild boar
, which was given the name ''Sus scrofa'' by
Carl Linnaeus Carl Linnaeus (; 23 May 1707 – 10 January 1778), also known after his Nobility#Ennoblement, ennoblement as Carl von Linné#Blunt, Blunt (2004), p. 171. (), was a Swedish botanist, zoologist, taxonomist, and physician who formalised binomi ...

Carl Linnaeus
in 1758; following from this, the formal name of the pig is ''Sus scrofa domesticus''. However, in 1777,
Johann Christian Polycarp Erxleben Johann Christian Polycarp Erxleben was a German German(s) may refer to: Common uses * of or related to Germany * Germans, Germanic ethnic group, citizens of Germany or people of German ancestry * For citizens of Germany, see also German nat ...
classified the pig as a separate
species In biology, a species is the basic unit of biological classification, classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individu ...

species
from the wild boar. He gave it the name ''Sus domesticus'', which is still used by some taxonomists.


History

Archaeological evidence suggests that pigs were
domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another group to secure a more predictable supply of resources from that sec ...
from wild boar in the
Near East The Near East ( ar, الشرق الأدنى, al-Sharq al-'Adnā, he, המזרח הקרוב, arc, ܕܢܚܐ ܩܪܒ, fa, خاور نزدیک, Xāvar-e nazdik, tr, Yakın Doğu) is a geographical term which roughly encompasses a transcontinental ...
in the
Tigris The Tigris () is the easternmost of the two great river A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at ...

Tigris
Basin,
Çayönü Çayönü Tepesi is a Neolithic The Neolithic period is the final division of the Stone Age, with a wide-ranging set of developments that appear to have arisen independently in several parts of the world. It is first seen about 12,000 years ...
, Cafer Höyük,
Nevalı Çori Nevalı Çori ( tr, Nevali Çori) was an early Neolithic The Neolithic period is the final division of the Stone Age The Stone Age was a broad prehistoric Prehistory, also known as pre-literary history, is the period of human history ...
being managed in the wild in a way similar to the way they are managed by some modern New Guineans. Remains of pigs have been dated to earlier than 11,400 years ago in
Cyprus Cyprus ; tr, Kıbrıs (), officially called the Republic of Cyprus,, , lit: Republic of Cyprus is an island country An island country or an island nation is a country A country is a distinct territory, territorial body or poli ...

Cyprus
. Those animals must have been introduced from the mainland, which suggests domestication in the adjacent mainland by then. There was also a separate domestication in China which took place about 8,000 years ago. In the Near East, pig husbandry spread for the next few millennia. It reduced gradually during the
Bronze Age The Bronze Age is a prehistoric Periodization, period that was characterized by the use of bronze, in some areas proto-writing, and other early features of urban civilization. The Bronze Age is the second principal period of the Three-age sys ...
, as rural populations focused instead on commodity-producing livestock. It was sustained urbanized regions, however.
DNA Deoxyribonucleic acid (; DNA) is a molecule File:Pentacene on Ni(111) STM.jpg, A scanning tunneling microscopy image of pentacene molecules, which consist of linear chains of five carbon rings. A molecule is an electrically neutral gro ...

DNA
evidence from subfossil remains of teeth and jawbones of Neolithic pigs shows that the first domestic pigs in Europe had been brought from the Near East. This stimulated the domestication of local European wild boar, resulting in a third domestication event with the Near Eastern genes dying out in European pig stock. Modern domesticated pigs have involved complex exchanges, with European domesticated lines being exported, in turn, to the ancient Near East. Historical records indicate that Asian pigs were introduced into Europe during the 18th and early 19th centuries. In August 2015, a study looked at over 100 pig genome sequences to ascertain their process of domestication, which was assumed to have been initiated by humans, involved few individuals, and relied on reproductive isolation between wild and domestic forms. The study found that the assumption of reproductive isolation with population bottlenecks was not supported. The study indicated that pigs were domesticated separately in Western Asia and China, with Western Asian pigs introduced into Europe, where they crossed with wild boar. A model that fit the data included a mixture with a now extinct
ghost population A ghost population is a population that has been inferred through using statistical techniques. Population studies In 2004, it was proposed that Maximum likelihood In statistics, maximum likelihood estimation (MLE) is a method of estimating E ...
of wild pigs during the
Pleistocene The Pleistocene ( , often referred to as the ''Ice Age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the earth’s most recent period of repeated glaciations. Before a change finally ...
. The study also found that despite back-crossing with wild pigs, the genomes of domestic pigs have strong signatures of selection at DNA loci that affect behavior and morphology. The study concluded that human selection for domestic traits likely counteracted the homogenizing effect of gene flow from wild boars and created domestication islands in the genome. The same process may also apply to other domesticated animals. In 2019, a study showed that the pig had arrived in Europe from the Near East 8,500 years ago. Over the next 3,000 years they then admixed with the European wild boar until their genome showed less than 5% Near Eastern ancestry, yet retained their domesticated features. Among the animals that the Spanish introduced to the
Chiloé Archipelago The Chiloé Archipelago ( es, Archipiélago de Chiloé, , ) is a group of islands lying off the coast of Chile Chile, officially the Republic of Chile, is a country in the western part of South America South America is a entir ...
in the 16th century, pigs were the most successful to adapt. The pigs benefited from abundant
shellfish Shellfish is a colloquial and fisheries Fishery is the enterprise of raising or harvesting fish and other aquatic life. Commercial fisheries include wild fisheries and Fish farming, fish farms, both in fresh water (about 10% of all catch) and t ...

shellfish
and
algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic Photosynthesis is a process used by plants and other organisms to convert Conversion or convert may refer to: Arts, entertainment, and media * Co ...

algae
exposed by the large
tide Tides are the rise and fall of sea level Mean sea level (MSL) (often shortened to sea level) is an average In colloquial, ordinary language, an average is a single number taken as representative of a list of numbers, usually the sum of ...

tide
s of the archipelago. Pigs were brought to southeastern North America from Europe by de Soto and other early Spanish
explorer Exploration is the act of searching for the purpose of discovery Discovery may refer to: * Discovery (observation) Discovery is the act of detecting something new, or something previously unrecognized as meaningful. With reference to scien ...

explorer
s. Escaped pigs became
feral in St. Kilda, Scotland, St Kilda, Scotland A feral animal or plant (from la, fera, 'a wild beast') is one that lives in the wild but is descended from Domestication, domesticated specimens. As with an introduced species, the introduction of ...

feral
and caused a great deal of disruption to
Native Americans Native Americans may refer to: Ethnic groups * Indigenous peoples of the Americas, the pre-Columbian peoples of North and South America and their descendants * Native Americans in the United States * Indigenous peoples in Canada, the indigenous p ...
. Feral pig populations in the southeastern United States have since migrated north and are a growing concern in the
Midwest The Midwestern United States, also referred to as the Midwest or the American Midwest, is one of four Census Bureau Region, census regions of the United States Census Bureau (also known as "Region 2"). It occupies the northern central part of ...
. Considered an invasive species, many state agencies have programs to trap or hunt feral pigs as means of removal. Domestic pigs have become feral in many other parts of the world (e.g. New Zealand and northern
Queensland Queensland ( ) is a state situated in northeastern Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the ...

Queensland
) and have caused substantial environmental damage. Feral hybrids of the European wild boar with the domestic pig are also very disruptive to both environment and agriculture (among the 100 most damaging animal species), especially in southeastern South America from Uruguay to Brazil's
Mato Grosso do Sul Mato Grosso do Sul () is one of the Midwestern states of Brazil. Neighboring Brazilian states are (from north clockwise) Mato Grosso, Goiás, Minas Gerais, São Paulo (state), São Paulo and Paraná (state), Paraná. It also borders the countries ...
and
São Paulo São Paulo (, ; Portuguese for 'Saint Paul') is a city in the Southeast Region, Brazil, Southeast Region of Brazil. Listed by the Globalization and World Cities Research Network, GaWC as an global city, alpha global city, the Municipalities of ...
. With around 1 billion individuals alive at any time, the
domesticated Domestication is a sustained multi-generational relationship in which one group of organisms assumes a significant degree of influence over the reproduction and care of another group to secure a more predictable supply of resources from that sec ...
pig is one of the most numerous large mammals on the planet.


Reproduction

Female pigs reach sexual maturity at 3–12 months of age and come into
estrus The estrous cycle (, originally ) is the set of recurring physiological changes that are induced by reproductive hormone A hormone (from the Greek Greek may refer to: Greece Anything of, from, or related to Greece Greece ( el, Ελλ ...

estrus
every 18–24 days if they are not successfully bred. The variation in ovulation rate can be attributed to intrinsic factors such as age and genotype, as well as extrinsic factors like nutrition, environment, and the supplementation of exogenous hormones. The gestation period averages 112–120 days. Estrus lasts two to three days, and the female's displayed receptiveness to mate is known as standing heat. Standing heat is a reflexive response that is stimulated when the female is in contact with the saliva of a sexually mature boar.
Androstenol Androstenol, also known as 5α-androst-16-en-3α-ol (shortened to 3α,5α-androstenol or 3α-androstenol), is a steroid , a steroid with 27 carbon atoms. Its core ring system (ABCD), composed of 17 carbon atoms, is shown with IUPAC The Inte ...
is one of the pheromones produced in the submaxillary salivary glands of boars that will trigger the female's response. The female cervix contains a series of five interdigitating pads, or folds, that will hold the boar's corkscrew-shaped penis during copulation. Females have
bicornuate uterus A bicornuate uterus or bicornate uterus (from the Latin ''cornū'', meaning "horn"), is a type of mullerian anomaly in the human uterus, where there is a deep indentation at the fundus (top) of the uterus. Pathophysiology A bicornuate uterus d ...
es and two conceptuses must be present in both uterine horns for pregnancy to be established. Maternal recognition of pregnancy in pigs occurs on days 11 to 12 of pregnancy and is marked by progesterone production from a functioning corpus luteum (CL). To avoid luteolysis by PGF2α, rescuing of the CL must occur via embryonic signaling of estradiol 17β and PGE2. This signaling acts on both the endometrium and luteal tissue to prevent the regression of the CL by activation of genes that are responsible for CL maintenance. During mid to late pregnancy, the CL relies primarily on luteinizing hormone (LH) for maintenance until parturition. Animal nutrition is important prior to reproduction and during gestation to ensure optimum reproductive performance is achieved. Archeological evidence indicates that medieval European pigs farrowed, or bore a litter of piglets, once per year. By the nineteenth century, European piglets routinely double-farrowed, or bore two litters of piglets per year. It is unclear when this shift occurred.


Behavior

In many ways, their behaviour appears to be intermediate between that of other artiodactyls and of
carnivores A carnivore , meaning "meat Meat is animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume orga ...
.Clutton-Brock, J., (1987). A Natural History of Domesticated Mammals. Cambridge University Press, Cambridge pp.73–74 Pigs seek out the company of other pigs and often huddle to maintain physical contact, although they do not naturally form large herds. They typically live in groups of about 8–10 adult sows, some young individuals, and some single males. Because of their relative lack of sweat glands, pigs often control their body temperature using behavioural thermoregulation. Wallowing, which often consists of coating the body with mud, is a behaviour frequently exhibited by pigs. They do not submerge completely under the mud, but vary the depth and duration of wallowing depending on environmental conditions. Typically, adult pigs start wallowing once the ambient temperature is around 17–21 °C (63–70 °F). They cover themselves from head to toe in mud. Pigs may use mud as a sunscreen, or as a method of keeping parasites away. Most bristled pigs will "blow their coat", meaning that they shed most of the longer, coarser stiff hair once a year, usually in spring or early summer, to prepare for the warmer months ahead. If conditions permit, pigs feed continuously for many hours and then sleep for many hours, in contrast to
ruminants Ruminants (suborder In biological classification, the order ( la, wikt:ordo#Latin, ordo) is # a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. The well-known ranks in descending order are: life, ...
which tend to feed for a short time and then sleep for a short time. Pigs are
omnivorous An omnivore () is an animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular ...
, and are highly versatile in their feeding behaviour. As they are foraging animals, they primarily eat leaves, stems, roots, fruits, and flowers. Pigs play an important role in regions where
pig toilet A pig toilet (sometimes called a "pig sty latrine Public Latrine at Athens' Roman Forum site. A latrine is a toilet or an even simpler facility that is used as a toilet within a sanitation system. For example, it can be a communal trench in th ...
s are employed. Pigs are highly intelligent animals, on par with dogs, and according to David DiSalvo's writing in ''
Forbes ''Forbes'' () is an American business magazine owned by Integrated Whale Media Investments and the Forbes family The Forbes family is one of the Boston Brahmins—a wealthy extended American family long prominent in Boston, Massachusett ...

Forbes
'', they are "widely considered the smartest domesticated animal in the world. Pigs can move a cursor on a
video screen A computer monitor is an output device that displays information in pictorial form. A monitor usually comprises the electronic visual display, visual display, electronic circuit, circuitry, casing, and power supply. The display device in modern m ...

video screen
with their snouts and understand what is happening onscreen, and even learn to distinguish between the scribbles they knew from those they saw for the first time."


Rooting

Rooting is an instinctual behavior in pigs that is characterized by a pig nudging its snout into something. Similar to a cat's kneading, rooting is found comforting. It first happens when piglets are born to obtain their mother's milk, and can become a habitual, obsessive behavior which is most prominent in animals
weaned Weaning is the process of gradually introducing an infant 222x222px, Eight-month-old sororal twin sisters An infant (from the Latin word ''infans'', meaning 'unable to speak' or 'speechless') is the more formal or specialised synonym ...
too early. Often, pigs will root and dig into the ground to forage for food. By means of rooting, pigs have been used to
till image:Geschiebemergel.JPG, Closeup of glacial till. Note that the larger grains (pebbles and gravel) in the till are completely surrounded by the matrix of finer material (silt and sand), and this characteristic, known as ''matrix support'', is d ...
farmland. Rooting is known to also be used as a means of communication. Nose rings that pierce the septum of the nose discourage rooting because they make the behavior painful. The breed known as the
kunekune The Kunekune is a small breed of domestic pig from New Zealand. Kunekune are hairy with a rotund build, and may bear Wattle (anatomy), wattles hanging from their lower jaws. Their colour ranges from black and white, to ginger, cream, gold-tip, b ...

kunekune
hardly ever roots, as it can sustain itself by feeding on nothing other than grass. Not having to root around in the soil to find underground food (e.g. tubers), it thus has evolved to, for the most part, not possess the instinct for rooting.


Nest-building

A behavioural characteristic of pigs which they share with carnivores is nest-building. Sows root in the ground to create depressions and then build nests in which to give birth. First, the sow digs a depression about the size of her body. She then collects twigs and leaves, and carries these in her mouth to the depression, building them into a mound. She distributes the softer, finer material to the centre of the mound using her feet. When the mound reaches the desired height, she places large branches, up to 2 metres in length, on the surface. She enters into the mound and roots around to create a depression within the gathered material. She then gives birth in a lying position, which, again, is different from other artiodactyls, which usually give birth in a standing position. Nest-building behaviour is an important part in the process of pre and post-partum maternal behaviour. Nest-building will occur during the last 24 hours before the onset of farrowing and becomes most intense during 12 to 6 hours before farrowing. Nest-building is divided into two phases: one of which is the initial phase of rooting in the ground while the second phase is the collecting, carrying and arranging of the nest material. The sow will separate from the group and seek a suitable nest site with some shelter from rain and wind that has well-drained soil. This nest-building behaviour is performed to provide the offspring with shelter, comfort, and thermoregulation. The nest will provide protection against weather and predators while keeping the piglets close to the sow and away from the rest of the herd. This ensures they do not get trampled on and that other piglets are not stealing milk from the sow. Nest-building can be influenced by internal and external stimuli. Internal hormonal changes and the completion of one nesting phase are indicators of this maternal behaviour. The onset is triggered by the rise in prolactin levels, which is caused by a decrease in progesterone and an increase in prostaglandin, while the gathering of the nest material seems to be regulated more by external stimuli such as temperature. The longer time spent on nest-building will increase pre-partum oxytocin.


Nursing and suckling behaviour

Pigs display complex nursing and suckling behaviour. Nursing occurs every 50–60 minutes, and the sow requires stimulation from piglets before milk let-down. Sensory inputs (vocalisation, odours from mammary and birth fluids and hair patterns of the sow) are particularly important immediately post-birth to facilitate teat location by the piglets. Initially, the piglets compete for position at the udder; then the piglets massage around their respective teats with their snouts, during which time the sow grunts at slow, regular intervals. Each series of grunts varies in frequency, tone and magnitude, indicating the stages of nursing to the piglets. The phase of competition for teats and of nosing the udder lasts for about one minute and ends when milk flow begins. In the third phase, the piglets hold the teats in their mouths and suck with slow mouth movements (one per second), and the rate of the sow's grunting increases for approximately 20 seconds. The grunt peak in the third phase of suckling does not coincide with milk ejection, but rather the release of oxytocin from the pituitary into the bloodstream. Phase four coincides with the period of main milk flow (10–20 seconds) when the piglets suddenly withdraw slightly from the udder and start sucking with rapid mouth movements of about three per second. The sow grunts rapidly, lower in tone and often in quick runs of three or four, during this phase. Finally, the flow stops and so does the grunting of the sow. The piglets may then dart from teat to teat and recommence suckling with slow movements, or nosing the udder. Piglets massage and suckle the sow's teats after milk flow ceases as a way of letting the sow know their nutritional status. This helps her to regulate the amount of milk released from that teat in future sucklings. The more intense the post-feed massaging of a teat, the greater the future milk release from that teat will be.


Teat order

In pigs, dominance hierarchies can be formed at a very early age. Piglets are highly precocious and within minutes of being born, or sometimes seconds, will attempt to suckle. The piglets are born with sharp teeth and fight to develop a teat order as the
anterior Standard anatomical terms of location deal unambiguously with the anatomy Anatomy (Greek ''anatomē'', 'dissection') is the branch of biology concerned with the study of the structure of organism In biology, an organism (from Ancient ...
teats produce a greater quantity of milk. Once established, this teat order remains stable with each piglet tending to feed on a particular teat or group of teats. Stimulation of the anterior teats appears to be important in causing milk letdown, so it might be advantageous to the entire litter to have these teats occupied by healthy piglets. Using an artificial sow to rear groups of piglets, recognition of a teat in a particular area of the udder depended initially on visual orientation by means of reference points on the udder to find the area, and then the olfactory sense for the more accurate search within that area.


Senses

Pigs have vision of approximately 310° and
binocular vision In , binocular vision is a type of in which an animal has two s capable of facing the same direction to perceive a single of its surroundings. Neurological researcher Manfred Fahle has stated six specific advantages of having two eyes rather t ...

binocular vision
of 35° to 50°. It is thought they have no eye accommodation. Other animals that have no accommodation, e.g. sheep, lift their heads to see distant objects. The extent to which pigs have colour vision is still a source of some debate; however, the presence of
cone cell Cone cells, or cones, are photoreceptor cells A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina The retina (from la, rete) is the innermost, light-sensitive layer of tissue of the eye of most ve ...

cone cell
s in the retina with two distinct wavelength sensitivities (blue and green) suggests that at least some colour vision is present. Pigs have a well-developed sense of smell, and use is made of this in Europe where they are trained to locate underground
truffles A truffle is the fruiting body of a subterranean ascomycete fungus, predominantly one of the many species of the genus ''Tuber (fungus), Tuber''. In addition to ''Tuber'', many other genera of fungi are classified as truffles including ''Geopor ...

truffles
. Olfactory rather than visual stimuli are used in the identification of other pigs.Houpt, K.A., (1998). Domestic Animal Behavior for Veterinarians and Animal Scientists. 3rd edition. Iowa State University Press, Ames. Hearing is also well developed, and localisation of sounds is made by moving the head. Pigs use auditory stimuli extensively as a means of communication in all social activities.Gonyou, H.W., (2001). The social behaviour of pigs. In "Social Behaviour in Farm Animals", eds. Keeling, L.J., and Gonyou, H.W. CABI, Oxford. Alarm or aversive stimuli are transmitted to other pigs not only by auditory cues but also by
pheromone A pheromone (from Ancient Greek ' "to bear" and hormone) is a secreted or excreted chemical factor that triggers a social response in members of the same species. Pheromones are chemicals capable of acting like hormones outside the body of the s ...

pheromone
s. Similarly, recognition between the sow and her piglets is by olfactory and vocal cues.


Breeds

Many
breed A breed is a specific group of domestic animals having homogeneous appearance (phenotype), homogeneous behavior, and/or other characteristics that distinguish it from other organisms of the same species. In literature, there exist several slight ...
s of pig exist, with different colors, shapes, and sizes. According to
The Livestock Conservancy The Livestock Conservancy, formerly known as the American Livestock Breeds Conservancy (ALBC) and prior to that, the American Minor Breeds Conservancy, is a nonprofit organization A nonprofit organization (NPO), also known as a non-business ent ...
, as of 2016, three breeds of pig are critically rare (having a global population of fewer than 2000). They are the
Choctaw hog#REDIRECT Choctaw hog {{Redirect category shell, 1= {{R from move {{R from alternative capitalization ...
, the Mulefoot, and the Ossabaw Island hog. The smallest known pig breed in the world is the , typically weighing about as a healthy, full-grown adult.


In agriculture

When in use as livestock, the pig is mostly farmed for its meat, pork. Other food products made from pigs include pork
sausage A sausage is a type of meat Meat is animal Animals (also called Metazoa) are multicellular eukaryotic organisms that form the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consum ...

sausage
(which includes
casing Casing may refer to an enclosing wikt:shell, shell, wikt:tube, tube, or surrounding material. It may also refer to: * Cartridge (firearms), shell enclosing the explosive propellant in ammunition * Casing (borehole), metal tube used during the dril ...
s that are made from the
intestine The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system The human digestive system consists of the gastrointestinal tract The gastrointestinal tract, (GI tract, GIT, d ...

intestine
s),
bacon Bacon is a type of salt-cured pork Pork is the culinary name for the meat of the Pig, domestic pig (''Sus scrofa domesticus''). It is the most commonly consumed meat worldwide, with evidence of pig animal husbandry, husbandry dating ba ...

bacon
, gammon,
ham Ham is pork Pork is the culinary name for the meat of a domestic pig The domestic pig (''Sus scrofa domesticus'' or only ''Sus domesticus''), often called swine, hog, or simply pig when there is no need to distinguish it from other ...

ham
and pork rinds. The head of a pig can be used to make a preserved jelly called
head cheese Head cheese or brawn is a cold cut Lunch meats—also known as cold cuts, luncheon meats, cooked meats, sliced meats, cold meats, and deli meats—are precooked or cured meats that are sliced and served cold or hot. They are typically ser ...

head cheese
, which is sometimes known as brawn.
Liver The liver is an organ Organ may refer to: Biology * Organ (anatomy) An organ is a group of Tissue (biology), tissues with similar functions. Plant life and animal life rely on many organs that co-exist in organ systems. A given organ's t ...
,
chitterlings Chitterlings (; sometimes spelled/pronounced chitlins or chittlins ) are a culinary dish usually made from the large intestines of a hog, although the intestines of cattle Cattle, or cows (female) and bulls (male), are the most common type ...
,
blood Blood is a body fluid Body fluids, bodily fluids, or biofluids are liquid A liquid is a nearly incompressible In fluid mechanics or more generally continuum mechanics, incompressible flow (isochoric process, isochoric flow) refers t ...
(for
black pudding Black pudding is a distinct regional type of blood sausage originating in the United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain,Usage is mixed. The Guardian' an ...
), and other
offal Offal (), also called variety meats, pluck or organ meats, is the Organ (anatomy), organs of a butchered animal. The word does not refer to a particular list of edible organs, which varies by culture and region, but usually excludes muscle. Offa ...

offal
from pigs are also widely used for food. In some religions, such as Judaism and
Islam Islam (; ar, اَلْإِسْلَامُ, al-’Islām, "submission o God Oh God may refer to: * An exclamation; similar to "oh no", "oh yes", "oh my", "aw goodness", "ah gosh", "ah gawd"; see interjection An interjection is a word or ex ...
, pork is a taboo food. Approximately 1.5 billion pigs are slaughtered each year for meat. The use of pig milk for human consumption does take place, but as there are certain difficulties in obtaining it, there is little commercial production. Livestock pigs are exhibited at
agricultural show An agricultural show is a public event exhibiting the equipment, animals, sports and recreation associated with agriculture and animal husbandry. The largest comprise a livestock show (a judged event or display in which selective breeding, breedi ...
s, judged either as stud stock compared to the standard features of each pig breed, or in commercial classes where the animals are judged primarily on their suitability for slaughter to provide premium meat. The is eaten and used to produce seat covers, apparel, and other items. In some developing and
developed nation Image:Imf-advanced-un-least-developed-2008.svg, 450px, Classifications by the International Monetary Fund, IMF and the United Nations, UN in 2008.A developed country, industrialized country (or post-industrial country), more developed countr ...

developed nation
s, the pig is usually raised outdoors in yards or fields. In some areas, pigs are allowed to
forage Forage is a plant material (mainly plant leaves and stems) eaten by grazing In agriculture Agriculture is the science, art and practice of cultivating plants and livestock. Agriculture was the key development in the rise of sedentism, se ...
in woods where they may be taken care of by
swineherd A swineherd is a person who raises and herds pigs The pig (''Sus domesticus''), often called swine, hog, or domestic pig when distinguishing from other members of the genus '' Sus'', is an omnivorous An omnivore () is an animal that has ...

swineherd
s. In industrialized nations such as the United States, pig farming has switched from the to large-scale intensive pig farms. This has resulted in lower production costs but can cause significant
cruelty Cruelty is pleasure in inflicting suffering or inaction towards another's suffering when a clear remedy is readily available. Sadomasochism, Sadism can also be related to this form of action or concept. Cruel ways of inflicting suffering may inv ...
problems. As consumers have become concerned with the humane treatment of livestock, demand for pasture-raised pork in these nations has increased.


As pets

Vietnamese Pot-bellied , country = Vietnam , distribution = Red River Delta , standard = , use = meat , weight = , maleweight = average: 50 kg (110 lb) , femaleweight = average: 48 kg (106 lb) , height = , maleheight = ...
pigs, a miniature breed of pig, have made popular pets in the United States, beginning in the latter half of the 20th century. In many respects, pot-bellied pigs are desirable and entertaining pets. They are considered intelligent, gregarious, and trainable. They lack the genetic hereditary weaknesses which commonly afflict certain pedigree cat and dog breeds, are generally quite sturdy, and have a reasonably affordable diet despite requiring large quantities of food. However, they can be strong-willed, defiant, and independent pets which will sometimes defy training. They require access to an outdoor space at all times, and depending on the individual pig, may become housebroken easily or never settle indoors. While hardy, an injured or sick pig will require costly surgery or larger than average quantities of medicine than most pets. Rescuing an abandoned fully-grown pig is usually a more reliable means of getting exactly what you expect than taking a piglet home. Pigs are highly intelligent, social creatures. They are considered
hypoallergenic Hypoallergenic, meaning "below average" or "slightly" allergenic is a term meaning that something (usually cosmetics Cosmetics are constituted from a mixture of chemical compounds derived from either natural sources or synthetically created ...
, and are known to do quite well with people who have the usual animal allergies. Since these animals are known to have a life expectancy of 15 to 20 years, they require a long-term commitment. Given pigs are bred primarily as livestock and have not been bred as companion animals for very long, selective breeding for a placid or biddable temperament is not well established. Pigs have radically different psychology to dogs and exhibit fight-or-flight instincts, independent nature, and natural assertiveness which can manifest as aggression towards children and a tendency to panic and lash out with little warning. Cats generally are safe around pigs as neither species has an incentive to express aggression or fear towards the other, although dogs will view pigs as prey animals and in turn, pigs will challenge dogs for food, leading to very violent fights.


Care

Male and female swine that have not been de-sexed may express unwanted aggressive behavior, and are prone to developing serious health issues. Regular trimming of the hooves is necessary; hooves left untreated cause major pain in the pig, can create malformations in bone structure and may cause him or her to be more susceptible to fungal growth between crevices of the hoof, or between the cracks in a split hoof. Male pigs, especially when left unaltered, can grow large, sharp tusks which may continue growing for years. Domestic owners may wish to keep their pigs' tusks trimmed back, or have them removed entirely. As prey animals, pigs' natural instinctive behavior causes them to have a strong fear of being picked up, resulting in the animal expressing stress through struggling and squealing, but they will usually calm down once placed back onto the ground. This instinctual fear may be lessened if the pig has been frequently held since infancy. When holding pigs, supporting them under the legs makes being held not as stressful for the animal. Pigs need enrichment activities to keep their intelligent minds occupied; if pigs get bored, they often become destructive. As rooting is found to be comforting, pigs kept in the house may root household objects, furniture or surfaces. While some owners are known to pierce their pigs' noses to discourage rooting behaviour, the efficacy and humaneness of this practice is questionable. Pet pigs should be let outside daily to allow them to fulfill their natural desire of rooting around.


In human medical applications

Pigs, both as live animals and a source of post-mortem tissues are one of the most valuable animal models used in biomedical research today, because of their biological, physiological, and anatomical similarities to human beings. For instance, human skin is very similar to the pigskin, therefore pigskin has been used in many preclinical studies. Porcine are used in finding treatments, cures for diseases, xenotransplantation, and for general education. They are also used in the development of medical instruments and devices, surgical techniques and instrumentation, and FDA-approved research. These animals contribute to the Three Rs (animal research), reduction methods for animal research, as they supply more information from fewer animals used, for a lower cost.


Xenotransplantation

Pigs are currently thought to be the best non-human candidates for organ donation to humans, and to date they are the only animal that has successfully donated an organ to a human body. The first successful donation of a non-human organ to a human body was conducted on 15 September 2021, when a kidney from a pig was transplanted to a brain-dead human and immediately started functioning similarly to a human kidney. The procedure, led by Dr. Robert Montgomery (physician), Robert Montgomery, used a donor pig that was genetically engineered to not have a specific carbohydrate that the human body considers a threat–Galactose-alpha-1,3-galactose. This followed an earlier major breakthrough when the carbohydrate was removed from genetically engineered mice. Besides similarity between pig and human organs, pigs are among the best animals suited for human donation due the lower risk of cross-species disease transmission. This is caused by pigs' increased Phylogenetics, phylogenetic distance from humans. Furthermore, they are readily available, and new infectious agents are less likely since they have been in close contact with humans through domestication for many generations.Taylor, L. (2007
Xenotransplantation
Emedicine.com
Some obstacles to successful organ donation from a pig to a human arise from the response of the recipient's immune system—generally more extreme than in allotransplantations, ultimately results in rejection of the xenograft, and in some cases results in the death of the recipient—including hyperacute Transplant rejection, rejection, acute vascular rejection, cellular rejection, and chronic rejection. Examples of viruses carried by pigs include porcine herpesvirus, rotavirus, parvovirus, and circovirus. Of particular concern are PERVs (porcine endogenous retroviruses), vertically transmitted viruses that embed in swine genomes. The risks with xenosis are twofold, as not only could the individual become infected, but a novel infection could initiate an epidemic in the human population. Because of this risk, the FDA has suggested any recipients of xenotransplants shall be closely monitored for the remainder of their life, and quarantined if they show signs of xenosis.FDA. (2006
Xenotransplantation Action Plan: FDA Approach to the Regulation of Xenotransplantation
Center for Biologics Evaluation and Research.
Pig cells have been engineered to inactivate all 62 PERVs in the genome using CRISPR#Editing, CRISPR Cas9 genome editing technology, and eliminated infection from the pig to human cells in culture.


Folklore

In the belief of traditional Irish fishermen, the pig is seen as a thing of bad luck and should not be mentioned.


Glossary of terms

Because the pig is a major List of domesticated animals, domesticated animal, English has many terms unique to the species: * ''barrow'' – a castrated male swine * ''boar'' – a mature male swine; often a wild or
feral in St. Kilda, Scotland, St Kilda, Scotland A feral animal or plant (from la, fera, 'a wild beast') is one that lives in the wild but is descended from Domestication, domesticated specimens. As with an introduced species, the introduction of ...

feral
swine * ''wikt:boneen, boneen'' – a very young pig (Ireland) * ''farrow'' (noun) – a litter of piglets * ''farrow'' (verb) – to give birth to piglets * ''gilt'' – a female pig that has never been pregnant or is pregnant for the first time * ''hog'' – a domestic swine, especially a fully-grown specimen * ''parcel'' – collective noun for pigs * ''pig'' – strictly, an immature swine; more generally, any swine, especially of the domestic variety * ''piglet'' – a very young pig * ''queen'' – a female pig that has never been mated * ''savaging'' – the act of a sow attacking her own piglets, sometimes killing and cannibalising them * ''shoat'' – a young pig, especially one that has been weaned * ''sounder'' – collective noun for pigs * ''sow'' – a mature female swine * ''swine'' (singular and plural) – hogs collectively or generally; also a Animal epithet, derogatory epithet#Dictionary of Agriculture 2006 reference, Dictionary of Agriculture (2006), "swine," 240. "''noun'' a collective term for pigs" * ''
swineherd A swineherd is a person who raises and herds pigs The pig (''Sus domesticus''), often called swine, hog, or domestic pig when distinguishing from other members of the genus '' Sus'', is an omnivorous An omnivore () is an animal that has ...

swineherd
'' – one who tends to swine raised as livestock; a pig farming, pig farmer


See also

*Farming *''Mycoplasma hyorhinis'' *Peccary (domestication) *Pet *Pigs in culture *Truffle hog *Xenotransfusion


Footnotes


References


Animal Welfare AVMA Policy on Pregnant Sow Housing
*
CAST Scientific Assessment of the Welfare of Dry Sows kept in Individual Accommodations- March 2009
*


External links


An introduction to pig keeping

British Pig Association

Globe and Mail article Canada's transgenic Enviropig is stuck in a genetic modification poke

Information on Micro Pigs


gilt pig breeders
JSR Genetics
Pig genetics company
Pig Sanctuary

Swine Care

Swine Study Guide
from UC Davis
The process of pig slaughtery
{{DEFAULTSORT:Pig Pigs Domestic pigs, Mammals described in 1777 Mammals as pets Livestock Pork Taxa named by Johann Christian Polycarp Erxleben