Miniature Pigs, also called Mini Pig, Micro Pig, Teacup Pig or Pygmy Pig, are small breeds of domestic pig, such as the Vietnamese Pot-Bellied pig, Göttingen minipig, Juliana pig, Choctaw hog, or Kunekune (and specimens derived by crossbreeding these breeds). Miniature pigs can usually be distinguished from other pigs by their possession of small perked-back ears, a pot belly, a swayed back, a chubby figure, a rounded head, a short snout, short legs, a short neck, and a tail with thick hair at the end. Typically, miniature pigs will range in weight from about 70 pounds (32 kg) to 300 pounds (140 kg).
In the 1960s, Chinese pigs that grew to be 68–91 kilograms (150–200 lb) were sent to zoos in Western cities and were used for medical research in the fields of toxicology, pharmacology, pulmonology, cardiology, aging, and as a source of organs for organ transplantation. These comparatively smaller pigs were easier to work with than larger pig breeds, which typically reach weights of 300–500 lb (140–230 kg).
In the mid-1980s, Keith Connell of 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. 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 piglets, but private owners soon began purchasing them as pets. Pet pot-bellied pigs started to appear everywhere; from New York apartment complexes to small suburban residences. 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. Today, most pot-bellied pigs are little to never purebred, as the pure breed is critically endangered.
The Miniature Potbellied Pig Registry Service, Inc (MPPRSI) was established in 1993 to provide a registry for those pigs who were pedigreed in the PPRSI and met the breed standard, when fully grown not being more than 60 centimetres (24 in) tall and weighing under 80 kilograms (180 lb). All of the foundation pigs were dual registered in the PPRSI and MPPRSI.
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. It is considered the smallest breed of domestic pig in the world.
Miniature pigs have been used for medical research, including toxicology, pharmacology, experimental surgery, pulmonology, cardiology, xenotransplantation, orthopedic procedures 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.  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.
Miniature pigs are commonly kept as pets. Realistic sizes of pigs vary from pig to pig; genetics drives the growth, along with appropriate nutrition and care. Domesticated miniature pigs can vary from 75 lbs to 150 lbs. It may be possible to reduce the risk of ending up with a large pig by looking at the pig's parents and grandparents if possible. However, since pigs can breed years before they fully mature, unscrupulous or ignorant breeders may show off parent pigs which are not fully grown themselves, so have not reached their full adult size.
Domesticated pigs are often trained to urinate and defecate in litter boxes. Typically, pine pellets or pine shreds are used.
In the U.S., laws may vary on if a pet pig can be kept, depending on the location. If there are no laws regarding pet pigs, some areas may consider a pig to be exclusively known as livestock; some towns and cities have ordinances disallowing farm animals within city limits. However, one can petition city councils and have outdated ordinances amended before a pig is introduced into a household, since many ordinances were put into place before the pot-bellied pig was even introduced to the U.S.
Pigs have been used in various types of animal-assisted therapy to perform duties in facilities including airports, hospitals, nursing homes, and special-needs schools, or as emotional support animals for individuals with conditions such as autism or anxiety and veterans with PTSD. Two well-known miniature pigs named Thunder and Bolt trained by children to certified animal therapy status have been put to work in a number of nursing homes, schools and a hospital.
Other notable references
The world's smallest wild pig species is the 71 centimetres (28 in) long wild pygmy hog which lives in Assam, India. It is a critically endangered wild species, not appropriate for domestication.
- "Basic Information Sheet: Miniature Pig". 20 July 2019.
- John Pukite (1999). A field guide to pigs. ISBN 1-56044-877-6.
- Sachs, DH; Galli, C (2009). "Genetic Manipulation in Pigs". Current Opinion in Organ Transplantation. 14 (2): 148–153. doi:10.1097/mot.0b013e3283292549. PMC 2687522. PMID 19469029.
- "Ag Facts: Swine". Oklahoma4h.okstate.edu. 1985-03-05. Archived from the original on 2016-04-27. Retrieved 2016-04-04.
- "History". Miniature Potbellied Pig Registry Service, Inc. Retrieved 4 February 2013.
- "Tea Cup Pigs, Yay or Nay? | SiOWfa15: Science in Our World: Certainty and Controversy". sites.psu.edu. Retrieved 2017-03-08.
- "Breed Standard". Archived from the original on 2015-10-05. Retrieved 2014-07-22.
- Bollen, PJA & Ellegaard, L.(1996). Developments in Breeding Göttingen Minipigs. In Tumbleson & Schook (eds.) Advances in Swine in Biomedical Research. New York: Plenum Press
- Høy-Petersen, J.; Smith, J. S.; Merkatoris, P. T.; Black, K. E.; Faivre, C. M.; Miles, K. G.; Tatarniuk, D. M.; Kraus, K. H. (2020). "Trochlear wedge sulcoplasty, tibial tuberosity transposition, and lateral imbrication for correction of a traumatic patellar luxation in a miniature companion pig: A case report and visual description". Frontiers in Veterinary Science. 7: 567886. doi:10.3389/fvets.2020.567886. PMC 7838352. PMID 33521073.
- Bode, G., Clausing P., Gervais, F., Loegsted, J., Luft, J., Nogues, V., & Sims, J. (2010) The utility of the minipigs as an animal model in regulatory toxicology. Journal of Pharmacological and toxicological methods, 62(3), 196-220.
- Svendensen, O. (2006). The minipig in toxicology. Experimental and Toxicologic Pathology, 57(5), 335-339.
- Dolgin, E. (2010). Minipig, Minipig, let me in. Nature Medicine, 16(12), 1349.
- Cooper, David K. C. (2017-03-08). "A brief history of cross-species organ transplantation". Proceedings (Baylor University. Medical Center). 25 (1): 49–57. doi:10.1080/08998280.2012.11928783. ISSN 0899-8280. PMC 3246856. PMID 22275786.
- Minimizing risk when buying a micro pig About Micro Pigs and their size - UK
- Teacup Pigs All the Rage, But Animal Welfare Group Urges People to do Homework Before Taking One Home October 28, 2009
- "Info/Resource - Pigs 4 Ever - Gifts, supplies and resources for Pot Bellied Pigs".
- "Changing city ordinance information- pig ordinance, pig regulations, pig approved homes, changing the law to allow pigs".
- Ross, Jane (2019-11-11). "World's first airport therapy pig hogs the limelight at San Francisco airport". Reuters. Retrieved 2021-01-30.
- Baskas, Harriet. "San Francisco airport introduces first 'therapy pig'". USA TODAY. Retrieved 2021-01-30.
- "Therapy Pigs Thunder and Bolt Are Happy to Trade Belly Scratches and Hugs for Smiles". PEOPLE.com. Retrieved 2021-01-30.
- Contributor, Pat McKnight. "Mini pig trains to work as therapy animal". Leader-Telegram. Retrieved 2021-01-30.
- "Therapy pigs are here to help humans". KidsNews. 2020-01-29. Retrieved 2021-01-30.
- WEAR, KATHRYN DANIEL (2018-02-19). "Therapy pigs in Northwest Florida trained to help veterans suffering from PTSD". WEAR. Retrieved 2021-01-30.
- Meet Rosie a Yucatan miniature pig May 10, 2009 NECN.com
- Mini pigs are big success on farm 15 October 2007 BBC News