According to the Field Guide to Pigs, there are well over 500 breeds of pigs in the world. The following section identifies the most common ones you might find on a farm.

The Poland China is from neither Poland or China. Instead it comes from Warren County in Ohio. A Polish man made the breed popular, though. This pig has white socks, a white snout, and a white tail. The ears usually hang well over the eyes. It has a quiet disposition and a rugged constitution. Males can easily get to 900 pounds. The largest Poland China, however, weighed a whopping 2,552 pounds.

The wild pig (Sus scrofa) can take advantage of any forage resources. Therefore, it can live in virtually any productive habitat that can provide enough water to sustain large mammals such as pigs. If there is increased foraging of wild pigs in certain areas, it can cause a nutritional shortage which can cause the pig population to decrease. If the nutritional state returns to normal, the pig population will most likely rise due to the pigs' naturally increased reproduction rate.[12]

The Online Etymology Dictionary provides anecdotal evidence as well as linguistic, saying that the term derives

Miss Piggy, Babe, and Porky Pig represent the domestic pig in entertainment, and "The Three Little Pigs", Piglet in the stories of A. A. Milne, Charlotte's Web, The Sheep-Pig, Zhu Bajie and Napoleon in George Orwell's Animal Farm are prominent examples of the domestic pig in literature.

The chester white is an all white pig with medium floppy ears. It should have no spots on it’s body. Originally, the chester white was developed in the US in Chester country, Pennsylvania. It’s basically a mix of some now extinct breeds.

There are four hoofed toes on each foot, or trotter, with the two larger central toes bearing most of the weight, but the outer two also being used in soft ground.[3]

Pigs that are allowed to forage may be watched by swineherds. Because of their foraging abilities and excellent sense of smell, they are used to find truffles in many European countries.

The domestic pig typically has a large head, with a long snout which is strengthened by a special prenasal bone and a disk of cartilage at the tip.[2] The snout is used to dig into the soil to find food, and is a very acute sense organ. The dental formula of adult pigs is 3.1.4.33.1.4.3, giving a total of 44 teeth. The rear teeth are adapted for crushing. In the male the canine teeth can form tusks, which grow continuously and are sharpened by constantly being ground against each other.[2]

Pigs have panoramic vision of approximately 310° and binocular vision of 35° to 50°. It is thought they have no eye accommodation.[45] Other animals that have no accommodation, e.g. sheep, lift their heads to see distant objects.[46] The extent to which pigs have colour vision is still a source of some debate; however, the presence of cone cells in the retina with two distinct wavelength sensitivities (blue and green) suggests that at least some colour vision is present.[47]

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It is entirely likely that the word to call pigs, "soo-ie," is similarly derived.

Pigs have health issues of their own. Pigs have small lungs in relation to their body size and are thus more susceptible than other domesticated animals to fatal bronchitis and pneumonia.[33] Some strains of influenza are endemic in pigs (see swine influenza). Pigs also can acquire human influenza.

Pigs use mud as a sunscreen, protecting their skin from ultraviolet light. They wallow in the mud to stay cool on hot days and keep parasites away.[citation needed]

They are also very social. In the wild, pigs live in close-knit groups called sounders, according to the San Diego Zoo. Sounders consist of one male, many females and their young. Males without a sounder will form their own herds or be solitary. Bearded pigs can have sounders with up to 300 members.

Domestic pigs are farmed primarily for the consumption of their meat called pork. The animal's bones, hide, and bristles are also used in commercial products. Domestic pigs, especially the pot-bellied pig, are sometimes kept as pets.

The smallest boar is the pygmy hog (Sus salvanius). It grows to a length between 1.8 and 2.4 feett (55 to 71 centimeters) and 9.8 inches (25 cm) tall from hoof to shoulder. The pygmy hog only weighs 14.5 to 21 lbs (6.6 to 9.7 kg), according to the San Diego Zoo.

Pigs can be aggressive in defending themselves and their young. Pig-induced injuries are thus not unusual in areas where pigs are raised or where they form part of the wild or feral fauna.[34]

Wild boars are not endangered, according to the International Union for Conservation of Nature’s Red List of Threatened Species. They are listed as "least concern" due to the wild pig's "wide range, abundance, tolerance to habitat disturbance and presence in many protected areas."

Pigs are mammals with stocky bodies, flat snouts, small eyes and large ears. They are highly intelligent, social animals, and are found all over the world. 

With around 1 billion individuals alive at any time, the domesticated pig is one of the most numerous large mammals on the planet.[3][4] Pigs are omnivores and can consume a wide range of food, similar to humans.[5] Pigs can harbour a range of parasites and diseases that can be transmitted to humans. Because of the similarities between pigs and humans, pigs are used for human medical research.[6]

Occasionally, captive mother pigs may savage their own piglets, often if they become severely stressed.[10] Some attacks on newborn piglets are non-fatal. Others may cause the death of the piglets and sometimes, the mother may eat the piglets. It is estimated that 50% of piglet fatalities are due to the mother attacking, or unintentionally crushing, the newborn pre-weaned animals.[11]

Pigs, boars and hogs are omnivores and will eat just about anything. Wild boars eat roots, fruit, rodents and small reptiles, according to National Geographic. Domestic pigs and hogs are fed feed that is made from corn, wheat, soy or barley. On small farms, pigs are often fed "slop,” which consists of vegetable peels, fruit rinds and other leftover food items. Sometimes, free-range pigs find their own food, according to Oklahoma State University.

The behaviour of domestic pigs resembles that of dogs and humans more than that of cattle or sheep. In many ways, their behaviour appears to be intermediate between that of carnivores and the more highly evolved artiodactyls.[35] Domestic pigs seek out the company of other pigs, and often huddle to maintain physical contact, although they do not naturally form large herds.[citation needed]

Long isolated from other pigs on the many islands of Indonesia, Malaysia, and the Philippines, pigs have evolved into many different species, including wild boar, bearded pigs, and warty pigs. Humans have introduced pigs into Australia, North and South America, and numerous islands, either accidentally as escaped domestic pigs which have gone feral, or as wild boar.

Pigs are one of four known mammalian species which possess mutations in the nicotinic acetylcholine receptor that protect against snake venom. Mongooses, honey badgers, hedgehogs, and pigs all have modifications to the receptor pocket which prevents the snake venom α-neurotoxin from binding. These represent four separate, independent mutations.[9]

The relatively short, stiff, coarse hairs of the pig are called bristles, and were once so commonly used in paintbrushes that in 1946 the Australian Government launched Operation Pig Bristle. In May 1946, in response to a shortage of pig bristles for paintbrushes to paint houses in the post-World War II construction boom, the Royal Australian Air Force (RAAF) flew in 28 short tons of pig bristles from China, their only commercially available source at the time.[19]

The Genetics Society of America (GSA), founded in 1931, is the professional membership organization for scientific researchers and educators in the field of genetics. Our members work to advance knowledge in the basic mechanisms of inheritance, from the molecular to the population level.

The genus Sus is currently thought to contain ten living species. A number of extinct species (†) are known from fossils.

Domestic Pig

Boars, pigs and hogs live all over the world, except for Australia, Antarctica, northern Africa and far northern Eurasia, according to the Encyclopedia of Life. For example, red river hogs (Potamochoerus porcus), also called bush pigs, are found in Africa; babirusas  (Babyrousa babyrussa), or pig deer, are found in Indonesia; and Visayan warty pigs (Sus cebifrons) come from the Philippines. 

In India, pigs have been domesticated for a long time mostly in Goa and some rural areas for pig toilets. This was also done in China. Though ecologically logical as well as economical, pig toilets are waning in popularity as use of septic tanks and/or sewerage systems is increasing in rural areas.

There are hundreds of breeds of the domestic pig (Sus scrofa domesticus).

Female hogs reach sexual maturity at 3–12 months of age and come into estrus every 18–24 days if they are not successfully bred. The gestation period averages 112–120 days.[10]

The Online Etymology Dictionary also traces the evolution of sow, the term for a female pig, through various historical languages:

Because the domestic pig is a major domesticated animal, English has many terms unique to the species.

This pig is completely white (or slightly pinkish) and exceptionally long. It actually has more ribs than other pigs (17 in total) and is known for its bacon-producing ability. It has lean meat, fast growth, and is very sturdy. The Danes were the first to create this breed, and it has spread throughout the world.

The ancestor of the domesticated pig is the wild boar, which is one of the most numerous and widespread large mammals. Its many subspecies are native to all but the harshest climates of continental Eurasia and its islands and Africa as well, from Ireland and India to Japan and north to Siberia.

In this overview of the domestic pig we’ll highlight some of the more unique and interesting facts about this charismatic barnyard animal. We’ll review some of the most common breeds found on farms across the world. Finally, we’ll show some of the studies that have been done on pig intelligence.

Pigs usually weigh between 300 and 700 lbs. (140 and 300 kilograms). Domestic pigs are often bred to be heavier, according to the San Diego Zoo. A hog named Reggie set a weight record of 1,335 lbs. (605.5 kg) in the Iowa State Fair’s “Biggest Boar” contest in 2012, according to the Des Moines Register. 

Most domestic pigs have rather a sparse hair covering on their skin, although woolly-coated breeds, such as the Mangalitsa, are raised.[4]