Miniature horses have a long history and a worldwide distribution. Their exact origins are obscure and they vary from country to country. But horses and ponies, bred-down through selective breeding techniques to become miniaturized horses, have been developed on every continent. In Europe they originated in the 17th Century, where pony breeds were bred as pets for the nobility and others were developed to work in the coal mines. The term ‘miniature horse' encompasses all of these breeds and is considered a breed in itself. The Falabella Horses are miniature horses from Argentina, South America and are one of the smallest breeds of horse. In South Africa, there is the South African Miniature Horse that is also now recognized as a distinct breed. There is also the Caspian Horse found in the Elburz Mountains of Iran, that is also a recognized distinct breed.
In the United States Miniature horses are enjoyed for both show and as companion animals and pets. Most are too small to be ridden except by very small children, but they can be hitched to carts. Similar to highly trainable dogs, many miniature horses are also quite skilled and can be trained. They are used as guide horses to assist the blind or those with impaired hearing, while others are trained for used in military work. Also similar to dogs is their life span. A miniature horse, like a miniature dog, will live about one third longer than a full-sized horse.
There are many different breed registries across the world for miniature horses. Some registries emphasis miniatures with horse characteristics while others promote pony characteristics. There are hundreds of shows and competitions ranging from the regional stage to worldwide events. Miniature Horses can compete in all sorts of classes including everything from halter, driving, and jumping, games and obstacle courses, to conformation and showmanship.
Miniature Horses have been known by a variety of names, with the most common being the Miniature Horse, Miniature Ponies, or the Mini Horse. Some are also called Toy Horses, Pigmy Horses, and Dwarf Horses. A few other less familiar titles include Tiny Horse, Midget Horse, and Miniature Toy Horse. Generally the smallest miniature horses will be about 18 1/2 to 19 inches, but the smallest miniature on record was a stallion named 'Little Pumpkin' that stood only 14 inches tall.
The first miniature horses originated in Europe in the 17th Century from pony breeds and were bred as pets for the nobility. In the 19th Century, they were also used as work horses in Wales, the English Midlands, and Northern European coal mines as pit ponies until the 1950's.
Around this time period, Lady Estella Hope bred miniature horses and most of the miniatures in the United States descend from the ‘Hope' line. The breed became popular in the United States in the 20th Century. Miniature horses in the USA added additional lines from other breeds such as the Hackney Horse and the Pony of the Americas. In 1972, the Shetland Pony Registry opened a special division for miniatures and in 1978, the American Miniature Horse Association was founded.
The most well-known of the miniature breeds is the Falabella from Argentina. The Falabella Horses are descended from Andalusian horses that were brought by early Spanish immigrants and allowed to roam free. They developed characteristics that suited the sparse landscape, resulting in smaller horses. Patrick Newell began a Falabella breeding program in the late 19th Century, and by inbreeding the smallest of his stock and adding Welsh Pony and Shetland lines, he developed the smallest horse breed in the world at 30 inches tall or smaller. The smallest horse on record was a Falabella that was 20 inches tall and weighed only 30 pounds!
Another distinct miniature horse breed is the Caspian Horse. Originating from the south end of the Caspian Sea, this little horse is closely related to the Arabian, and may be the ancestor of all modern hot blooded breeds of horses.
In 1978, The American Miniature Horse Association (AMHA) was formed. It is now the only registry in existence that deals exclusively with true Miniatures, 34 inches and under. Ponies over 34 inches are not considered Miniatures; they were not in the beginning, and they are not today (excluding the AMHR miniatures that measure 38 inches and under). n the AMHR, Miniatures cannot exceed 38 inches at the withers (which the AMHR defines as located at the last hair of the mane). There are two divisions in AMHR: the "A" division for horses 34 inches (86 cm) and under, and the "B" division for horses 34 to 38 inches (86 to 97 cm). The AMHA requires that horses stand under 34 inches. Horses of any eye or coat color, and any form of white markings, are allowed to be registered. The AMHA standard suggests that if a person were to see a photograph of a miniature horse, without any size reference, it would be identical in characteristics, conformation, and proportion to a full-sized horse. According to the AMHR, a "Miniature should be a small, sound, well-balanced horse and should give the impression of strength, agility and alertness. A Miniature should be eager and friendly but not skittish in disposition.
While dogs are the “norm” for guide animals, more and more people are using miniature horses. It’s a great alternative for someone who’s allergic to dogs, or who just prefers a horse. Want more information? Check out the Guide Horse Foundation.
The AMHA believes, quite staunchly, that nothing over 34” should be considered a miniature horse. The AMHR has two height divisions, one for 34” and under and one for 34” to 38” They are generally quite hardy, often living longer on average than some full-sized horse breeds; the average life span of miniature horses is from 25 to 35 years. However, there are also some health issues that are more frequently found in miniature horses than their full-sized relatives. Overfeeding is a common problem in miniature horses, leading to obesity; this is especially true when owners are used to owning full-sized horses. Dental issues, including crowding, brachygnathism (overbites) and prognathism (underbites) are frequently seen, due to having the same number of teeth in a much smaller mouth. They can also experience retention of deciduous teeth (baby teeth) and sinus problems from overcrowding. The combination of a propensity for overeating and dental problems can lead to an increased occurrence of colic. A major metabolic problem seen more frequently in miniature horses is hyperlipemia, where an appetite-reducing stressor can cause the body to break down significant amounts of fat, overwhelming the liver and potentially leading to liver failure. Reproduction is also more difficult in miniature horses, with a higher incidence of difficult births and a greater potential for eclampsia. The majority of the health problems seen more frequently in miniature horses are easily rectified with proper feeding and maintenance. horses. Minis have the same gestation period as their full-sized kin -- 11 months or 345 days.
The University of Kentucky Animal Genetic Testing and Research Laboratory (AGTRL) is now offering DNA-based tests for four mutations in the aggrecan gene (ACAN) associated with dwarfism in Miniature Horses. John Eberth, MS, a PhD student of Ernie Bailey, PhD, professor in genetics and genomics at the UK Gluck Equine Research Center, discovered the mutations.
It is important to note that these mutations are not associated with another type of dwarfism known as skeletal atavism seen in Miniature Horses and Shetland Ponies. The ACAN mutations are also not associated with the osteochondrodysplasia dwarfism found in some breeds such as Friesians. The four identified mutations are designated D1, D2, D3, and D4. The normal copy of the gene is designated as N.
Dwarfism is a concern within the miniature horse world. Dwarf horses, while often setting world records for size, are not considered to have desirable traits, generally have incorrect conformation, and may have significant health and soundness issues. Therefore, many miniature horse registries try to avoid accepting minis affected by dwarfism for breeding stock registration. In 2014, a commercial DNA test became available for one set of dwarfism mutations. The four mutations of the ACAN gene are known to cause dwarfism or aborted fetuses in miniature horses. The test does not detect the mutations that cause skeletal atavism in miniature horses and some ponies, or the osteochondrodysplasia dwarfism seen in some horse breeds.
The oldest living horse on record was a miniature horse affected by dwarfism named Angel who lived with the Horse Protection Society of North Carolina and lived to be over 50. The current record holder for the world's smallest horse is also a horse affected by dwarfism, Thumbelina, who is fully mature but stands 17 inches (43 cm) tall and weighs 60 pounds (27 kg). Though she has received considerable publicity, her owners have publicly stated that she will not be bred. In 2010 a 6-pound (2.7 kg) miniature horse foal named Einstein challenged Thumbelina for the title of the World's Smallest Horse in part based upon the idea that there should be a separate world record category for the smallest non-dwarf horse.
Mini’s tend to have fewer lameness issues in general. Some of the more common issues include:
1) Angular Limb Deformities – This would also be known as “crooked-leg” syndrome. This occurs in minis due to laxity of the soft tissue structures around joints, incomplete ossification of bones and problems with the growth plates. Nutrition, prematurity and trauma are often highly associated. Diagnosis is made by physical exam and radiographs and treatment is based on rest, appropriate farrier work and sometimes surgery. Because minis reach their growth potential earlier than large breeds, surgical or medical correction of angular limb deformities must occur earlier in life.
2) Upward Fixation of the Patella (locking stifle) – In a normal horse, the patella (knee cap) slides up and down. However, in some horses, due to conformation or inflammation, the patella slides up and becomes stuck. The horse would then demonstrate an inability to bring the leg forward. The toe often drags behind the leg and the fetlock (ankle) will be flexed, but not the hock or stifle. Usually, this can be corrected by asking the horse to move backwards, sometimes the owner or vet has to manually fix the leg. The condition is often hereditary in minis and treatments, such as stifle blistering, anti-inflammatories or surgery are required to prevent the fixation from continuing to occur.
3) Luxation of the Patella – This occurs when the patella slips to the outside of the stifle (knee) joint. This seems to be a congenital problem in mini’s due to an underdevelopment of one of the bones of the stifle. These mini’s present with a stiff gait and inability to flex the stifle. The only really successful treatment involves surgery, otherwise severe arthritis can form.
Miniature horses, in general, seem more resistant to laminitis; however, as with any horse, if they are overfed, laminitis can occur – and if it occurs, it can be severe. Diet management is a must. One must also be careful with non-steroidal anti-inflammatories for the treatment of lameness, as only a very small dose is required and if excess is administered, severe gastric and intestinal ulceration(s) can result.
Minis are susceptible to the same respiratory diseases as large breed horses, such as flu, rhino and strangles. If minis spike a fever, they often go off feed, which, as we discuss further later, can be life threatening for them. Other clinical signs include: cough, nasal discharge and enlarged lymph nodes. One condition that is more common in minis would be sinusitis.
1) Sinusitis – Mini’s have very small sinuses for their size, with large roots on their cheek teeth which can prevent normal sinus drainage. Signs of sinusitis include facial swelling, nasal discharge and sometimes fever. Diagnosis is made by physical exam and radiographs. Treatment relies on antibiotics, dental work and sometimes surgery to flush out the sinus.
Teeth and Jaws
Many minis have poor conformation to their mouth, which promotes many dental disorders. Malocclusions (the teeth do not meet correctly) and maleruptions (the baby teeth are not lost correctly) are common. Sow mouth and parrot mouth conformations are also common. Routine dental exams become more important in minis, even though many do not wear a bit; as if these conditions go unchecked, the horse cannot eat well, loses weight and may be more predisposed to colic.
Veterinarians face unique problems in the diagnosis and treatment of colic in minis. Miniature Horses often do not show a lot of the classic signs of pain. They may only be off feed or have a decreased fecal production. Diagnosis is often based on a physical exam and response to therapy. Due to their small size, a rectal exam is often not performed. It is also difficult to siphon fluid out of the stomach because of the small tube necessary. Ultrasound and radiography, however, are easier due to their small size. Certain types of colics that minis are more predisposed to include the following:
1) Fecaliths – Fecaliths are impactions formed by improper fecal ball production and often contain hair, sand and other foreign objects (twine, plastic etc.).
2) Enteroliths – Enteroliths are hard, “rock-like” concretions that form in the intestinal tract, often associated with sand and high alfalfa diets. Both of the above often require surgery for resolution.
3) Sand Colics – Sand Colics are common in minis as they tend to scrounge for every last morsel. Avoid feeding from the ground and test the manure by performing a Sands Test (floating feces in water in a clear Ziploc bag, and watching for sand settling out). You should perform this test often and treat with psyllium, if necessary. An instructional video of how to perform a Sands Test is also located in our blog.
Hyperlipemia and Hepatic Lipidosis
Hyperlipemia is a metabolic condition initiated when a horse goes off feed. Horses go
off feed for a variety of reasons, including: illness, colic, late pregnancy / lactation, or starvation. When the feed intake decreases, fat stores are metabolized and excess fats will be seen in the blood, actually giving the blood serum a milky white appearance. The fat stores are broken down for energy in the liver. This is not a very efficient process, and eventually, when the liver cannot cope, the fat starts building up in the liver, leading to a condition called Hepatic Lipidosis.
Both of these conditions present as mild colic (from a swollen liver), jaundice, swollen legs and sometimes neurologic signs. Treatment can be difficult and relies on intravenous nutrition and then getting the horse eating again. The prognosis is quite poor with a mortality rate of 60 to 100 percent, so if your mini goes off feed for more than 24 hours, it is imperative that they be evaluated.
The small size of miniatures leads to some special considerations with regards to breeding and foaling. Collecting semen is more of a challenge, as is artificial insemination due to the small size of the mares’ reproductive tract. Most miniature mares are bred by natural cover. Monitoring the mares reproductive cycle can also be challenging as rectal exams cannot be performed in many small mares. The Wisconsin Equine Clinic & Hospital has designed a rectal probe that can be used without an arm being inserted and the cycle can be effectively evaluated. The same probe can safely be used for pregnancy exams at 14 to 18 days. Later in pregnancy, a trans-abdominal ultrasound can be used, or blood testing of estrone sulfate levels.
Miniature horses have a higher abortion rate than large breed horses. These abortions often occur after six months of gestation and often occur due to a malformed fetus, twins or a twisted umbilical cord. Minis also have a higher risk of dystocia, as many foals are born with a domed forehead which can often become stuck in the pelvic inlet.
Feeding miniature horses does not need to be difficult. The same principles apply to minis as apply to large breeds. Fresh water needs to be available at all times. Carbohydrates are the primary energy source, and, 50 percent or more of the diet should be forage (hay, grass, hay cubes).
The main challenge owners face is estimating body weight – and most owners underestimate weight by 30 to 50 pounds and therefore, tend to overfeed. To maintain body weight, minis need 1.5 to 3 percent body weight fed per day. Owners are encouraged to weigh their hay and feed no more than 1.25 pounds of grain per 250 pounds of body weight. Again – weigh the grain so it is not being overfed. Most minis should not have free access to pasture, unless the pasture is very sparse. Limit the access to grass to short periods one to two times daily. An estimate of grass eaten needs to be factored into the total daily ration, as well.
Dwarfism is defined as the “underdevelopment of the body characterized by an abnormally short stature often with underdeveloped limbs and other defects.” Dwarfism is a recessive genetic disorder where both parents must pass on an affected allele to the offspring. Equine dwarfism is most prevalent in the miniature horse breed, but has also been recorded in friesians, mustangs, shetland ponies, and even the miniature donkey.
In the miniature horse breed, dwarfism is estimated to be in over 50% of the population and affects all miniature horse bloodlines. Unlike many other equine genetic disorders there is no test for owners and breeders to cull their breeding stock. Dwarfism cannot be culled by phenotypical characteristics because of the fact that many of the carriers are normal phenotypically and have even lead successful show careers. The only successful way of culling the carriers is to retire broodmares and geld stallions that have already produced a dwarf foal. Both the lack of genetic testing and difficulty in culling the breed phenotypically makes breeding often a heartbreaking task.
Another reason why breeding miniature horses is a daunting task is because there are multiple types of dwarfs. There are four known possible types of dwarfism which are characterized by the severity of their phenotypical characteristics. The types are as follows: diastrophia, achondroplasia, brachiocephalia, and the most lethal of them all, hypochondrogenesis. Diastrophia, translates into, “twisted limb,” but is not always the case. It has been recorded in both miniature horses and friesians. Diastrophia is characterized by twisted extremities, cow hocks, ligament deformities, pot bellies, weak hind ends, and roach backs. The main body of the diastrophic dwarf is often compacted due to the regular sized organs and genitals, which results in a pot bellied appearance. Arthritis is often seen in diastrophics at an early age. The legs of the diastrophic dwarf are often longer than normally expected in dwarves.
Achondroplasia, the second type of dwarfism, translates into, “short extremities.” Achondroplasia is the most common form of dwarfism and is estimated to be in over 25-50% of miniature horses. Achondroplasia dwarves have normal sized bodies and heads, but noticeably smaller upper legs and ears. The backs of the Achondroplasia dwarf are often longer than the normal miniature horse’s and their legs are sometimes contracted and even have loose tendons. Achondroplasia dwarves are able to live fairly normal lives but often times are afflicted with premature arthritis.
Brachiocephalia, the third type of dwarfism, is the most popularly documented form of dwarf by popular culture today. One of the most popular dwarves by popular culture is Thumbelina, who at ten years old stands at seventeen and a half inches tall.
Brachiocephalia is a varied form of dwarfism in the terms of expression. It can cause multiple defects at varied extents. Individual dwarves may not express the same traits at the same expression as another.
Brachiocephalia can cause misaligned jaws, obstructed nasal passages, protruding roach backs, and ligament disorders. Brachiocephalia dwarves often times have shorter life spans due to heart and organ failure.
Hypochondrogenesis, the fourth type of dwarfism, is the most fatal form of dwarfism. Hypochondrogenesis dwarves are aborted before birth, often times before they reach the embryonic stage. The foals many times have an exaggerated pot belly and cranium with short legs. The bones of the hypochondrogenesis dwarf are not ossified. Hypochondrogenesis dwarfism is thought to be caused by more than one form of dwarfism in one foal.
The birth of a dwarf foal is often times an accident and unexpected. The parents of a dwarf foal must be carriers of the dwarf gene. When bred together the offspring have a 25% chance of being a non-carrier, a 50% of being a carrier, and a 25% of being a dwarf. Seventy five percent of the time the dwarf gene will be passed on to their offspring. The breeding of two carriers or dwarves of different types will never produce a dwarf foal because of the lack of the same dwarf gene.
As a miniature horse breeder I began researching equine dwarfism when my breeding stock continued to foal dwarves. As of 2010, there have been six dwarf foals born: Simon, Trae, Boomer, Wendall, Teddy, and Connor. As a miniature horse owner it is my duty to educate the population of horse owners on the types and traits of dwarfism and also the genetics surrounding it. https://jcpminiatures.weebly.com/equine-dwarfism.html