Miniature pig

A miniature pig, minipig or micro-pig is a type of domestic pig characterised by its unusually small size but has no formal definition and can cover a variety of breeds.^[1][2] Some miniature pigs – such as the Cerdo Cuino of Mexico, the Lon I of Vietnam, the Ras-n-Lansa of Guam in the Marianas Islands and the Wuzhishan of Hainan Island in China – are traditional breeds of those areas.^{[3]: 238 [4]: 714} Many others have been selectively bred since the mid-twentieth century specifically for laboratory use in biomedical research; among these are the Clawn and the Ohmini of Japan, the Czech Minipig, the German Göttingen Minipig, the Lao-Sung of Taiwan, the Russian Minisib, the extinct Minnesota Miniature of the United States and the Westran of Australia.^[5]: 7 Some minipigs have been bred to be marketed as companion animals.^[4]: 652

A miniature sow attempting to mount another

Young pig on the streets

Miniature pigs generally reach their full size in about four years, and may live for up to fifteen. Some may reach a height of 50 cm (20 in) at the shoulder and a body length of 100 cm (40 in).^[6]

Young miniature pigs are sometimes sold as so-called ‘Teacup Pigs’ as pets.^[7][2] However, this term is used loosely and can refer either to young miniature pigs or piglets from larger breeds that have been underfed.^[1][7] Due to these breeding practices and the frequency of owners surrendering pigs when fully grown, the practice of selling miniature pigs as pets or as ‘teacup pigs’ is considered by some to be cruel.^[7][2][1][8]

History

The first mini pig breed developed in the United States was the Minnesota Miniature, which emerged in the 1940s.^[9][10]

In the 1960s, Vietnamese Pot-bellied pigs that grew up to 91 kilograms (200 lb) were sent to zoos in Western cities^[11] and were used for medical research in the fields of toxicology, pharmacology, pulmonology, cardiology, aging, and as a source of organs for organ transplantation.^[12] These comparatively smaller pigs were easier to work with than larger pig breeds, which typically reach weights of 600 lb (270 kg).^[13]

Beginning in the late 1960s at the Institute of Animal Breeding and Genetics (Institut für Tierzucht und Haustiergenetik) at the University of Göttingen, Germany, the Göttingen minipig was developed by crossbreeding the Minnesota minipig, the Vietnamese Pot-Bellied pig and the German Landrace pig.^[14]

In the mid-1980s, the Bowmanville Zoo in Ontario imported breeding Vietnamese Pot-Bellied pigs to Canada, which became the foundation for the pot-bellied pig in North America.^[15] The breed is known for its small stature, swayed back, and pronounced pot belly. Because of custom laws, only their offspring could be sold in the United States. U.S. zoos were the main target for the offspring.^[16][17][18]

Up to five additional imports were made in the following 10 years. To track the pedigrees, the Potbellied Pig Registry Service, Inc (PPRSI) was created to preserve these bloodlines and establish a breed registry in the United States. This registry was dissolved in the late 1990s.^[15] Today, most pot-bellied pigs are seldom to never purebred, as the pure breed is critically endangered.

Use

Miniature pigs have been used for medical research, including toxicology, pharmacology, experimental surgery, pulmonology, cardiology, xenotransplantation, orthopedic procedures^[19] and aging studies. Mini pigs are mainly used for biochemical, anatomical, and physiological similarities to humans. They are also quick to develop, making it easier to breed and have more genomic background compared to other animal models of toxicology. Today, more than 60,000 pigs are used for scientific research.^[20][21][22] For example, scientists are working on studying the possibility of utilizing pig hearts for human heart organ transplants, and work has been done to genetically modify the tissues of pigs to be accepted by the human immune system.^[23]

Miniature pigs are occasionally kept as companion animals, and some have been bred specifically to be marketed for this purpose.^[4]: 652

Pigs have been used in various types of animal-assisted therapy.^{[24][25][26][27][28][29]}

Breeds

Among the naturally-occurring traditional breeds of miniature pig are the following:

Local name(s)	English name if used	Country	. Notes	. Image
Ashanti Dwarf[3]: 206		Ghana
Bakosi[3]: 206		Cameroon
Bamaxiang[3]: 181		Guangxi, China
Chin[3]: 189		Myanmar
Cuino		Mexico	possibly extinct[3]: 239
Ghori[3]: 173		north-east India Bhutan Bangladesh
Lon Co		Vietnam	central Vietnam[3]: 188
Lon I	"Vietnamese Pot-bellied"	Vietnam	traditional breed, formerly numerous, now gravely endangered
Ras-n-las		Guam[4]: 606

Among the modern breeds created specifically for laboratory use are the following:

Name(s)	Country	Notes	Image
Clawn	Japan	bred from 1978 at Kagoshima University from Landrace x Large White, Göttingen Miniature and Ohmini[5]: 7 [4]: 580 [3]: 193
Froxfield Pygmy		United Kingdom[3]: 115
Göttingen Minischwein Göttingen Minipig	Germany	bred in the early 1960s at Göttingen University from small Vietnamese pigs and Minnesota Miniature; white variant developed by crossing with German Landrace[3]: 151
Hanford Miniature[3]: 151	United States
Munich Miniature[3]: 151	Germany
Ohmini	Japan	bred from the 1940s from Chinese pigs and Minnesota Miniature[3]: 193
Yucatan Miniature[3]: 238
Yucatan Micropig[3]: 238