Sus scrofa domesticus
A miniature pig is a breed of pig developed and used for medical research or for use as a pet. These smaller pigs were first used for medical research in Europe before being introduced to the United States in the 1980s. Since then, the animals have been used in studies by scientists around the world, and have also risen and fallen in popularity as unusual pets.
In the 1960s, pigs that grew to be 150–200 pounds (68–91 kg) were sent to zoos in Western nations and were used for medical research in the fields of toxicology, pharmacology, aging, and as a source of organs for organ transplantation. These small pigs were easier to work with than the larger farm pigs, which typically reach weights of 1000 pounds. Potbellied pigs also became a fixture in many zoological parks where their small stature, sway backs, and potbellies attracted the attention of visitors. The purchase of a few potbellied pigs by wealthy pet owners helped start a new trend in pet pigs.
The popularity of miniature pigs grew in the 1980s, with pet potbellied pigs appearing everywhere from New York apartment complexes to small hobby farms. However, the trend was short-lived, mostly due to city ordinances forbidding raising farm animals within the city limits. Furthermore, many owners came to realize that even a 165 pound pig was difficult to handle in most housing situations.
The 1990s and 2000s saw a rising trend of marketing pet pigs that were supposed to be much smaller than even the potbellied pigs, and therefore suitable pets for house and apartment owners. While multiple animal protection groups and pig breeders question or deny the existence of true "miniature pigs", there are currently breeders selling piglets claimed to be miniature pigs in North America and in the United Kingdom.
In the mid-1980s, Keith Connell of the Bowmanville Zoo in Ontario imported breeding Potbellied Pigs to Canada, which became the foundation for the Potbellied Pig in North America. Because of customs laws, only their offspring could be sold in the United States. US zoos were the main target for the piglets, but private owners soon began purchasing them as pets. 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.
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 15 inches (38 cm) tall and weighing under 55 pounds (25 kg). All of the foundation pigs were dual registered in PPRSI and MPPRSI.
In the UK, British micro pigs have been bred since 1992. Chris Murray, of Devon, England, spent 9 years on his Pennywell farm crossbreeding the Vietnamese Potbelly with the kunekune (a New Zealand pig weighing around 200 pounds (91 kg)), the Gloucestershire Old Spots (600 pounds (270 kg)) and the Tamworth (800 pounds (360 kg)) in an effort to create a smaller pig that would make a suitable pet. After 24 generations he came up with his own version of the miniature pig, which he originally called a Pennywell and then later the "teacup pig", apparently after discovering that they shared his love of tea. Murray unveiled this miniature pig in 2007 and began selling teacup pigs in pairs as pets to anyone who could afford them. An English woman named Jane Croft saw the teacup pigs and decided to breed and market them herself. Helped by sales to a few British celebrities, her business took off; she has since appeared on television talk shows displaying teacup pigs and touting their affection and intelligence. Miniature pigs bred in the United Kingdom are typically sold in pairs for US$1000 or more, not including transport.
There are also other opinions in debate about teacup pigs. Several micro pig owners have come forward with pictures of healthy adults that weigh under 40 Lbs. and believe that there are several animal activist groups pushing their own agenda and misleading people about the validity of teacup pigs. 
Miniature pigs, also known as micro pigs, pocket pigs, or teacup pigs, have seen an increase in popularity in being kept as pets, especially following Paris Hilton's purchase of one in 2009. They are intelligent animals and can be house-trained. They do not shed and tend to keep themselves clean.
Micro pigs can potentially make great pets, but there are considerably more risks involved when buying a micro pig over other common pets, such as cats or dogs. The biggest concern is that, since there is no established breed of "teacup pig", there is no guarantee that the pig sold as such will actually stay small. The risk of ending up with a large pig can be somewhat minimized by looking at the pig's parents and grandparents if possible. If they are on the smaller side, the odds are better that the pig will remain small. 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. Some breeders may falsely claim that a mini-pig is guaranteed to stay under a certain weight, and sometimes will recommend a diet regimen that starves the animal and unnaturally stunts its growth.
In 2012, the Juliana Pig Association & Registry (JPAR) was officially founded. This registry is concerned with the lineage and breeding of a subset group of miniature pigs called Juliana pigs. JPAR records lineage, size, and age on every pig entered and has an online database that is open to the public. JPAR has a breed standard, Code of Ethics for responsible breeding, and consequences to falsification of information for farms that make false claims about their pigs. As JPAR grows so does the consistency of this particular breed of miniature pig.
Some towns and cities have ordinances disallowing farm animals within city limits; a pig is usually considered a farm animal regardless of its size. As well, many small animal vets will not treat pigs. Since these animals have a life span of 15 to 20 years, they require long term commitment. Due to their ability to bond, combined with their need for attention, people who have limited time for a pet may find a pig far more than they can handle. Additionally, if pet pigs are not properly trained when they are young, just like a dog they can strive for dominance and become aggressive.
There are multiple animal rescue organizations set up to find new homes for pet pigs which have grown too large or otherwise unmanageable for their owners. In 2009, pig sanctuaries took in approximately 300,000 pigs which were surrendered by their owners, and abandoned pigs that cannot be rehomed are often euthanized.
Other notable references
- 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.
-  - Miniature Potbellied Pig Registry Service, Inc.
- Facts about Teacup Mini Potbelly Pigs
- The Truth about "Tea Cup" Pigs
- "History". Miniature Potbellied Pig Registry Service, Inc. Retrieved 4 Feb 2013.
- About Miniature Potbellied Pigs - Miniature Potbellied Pig Registry Service, Inc.
- Adorable ‘teacup pigs’ are latest hit with Brits By Mike Celizic TODAY contributor, 10/7/2009 9:19:24 AM ET
- Teacup Pigs the other story from happy owners.
- The Trouble with Teacup Pigs Andrew David Thaler, on October 14th, 2012
- Mini Pig Care guide
- You must have been told a porky: 'Micro' pig grows to 25 stone and takes over its owners' home By Daily Mail Reporter PUBLISHED: 12:51 EST, 27 July 2012 | UPDATED: 15:00 EST, 27 July 2012
- 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
- "Instead of providing breed-appropriate feed and portions, her breeder recommended tiny, toy breed puppy-sized food and water bowls." 
- Juliana Pig Association and Registry
- Pot Bellied Pigs as Pets
- Meet Rosie a Yucatan miniature pig May 10, 2009 NECN.com
- Mini pigs are big success on farm 15 October 2007 BBC News