Whilst the exact origin of the modern Miniature Horse is unclear, selective breeding of pony stock breeds such as the Shetland pony for a smaller size is most likely. Pony breeds, typically considered an equine under 14.2 hands or 58 inches in height, have been around for hundreds of years. Most of their evolutionary selection has been shaped by harsh natural climates and limited feed sources.
The Miniature Horse registry is based solely around height. Registries won’t allow membership to a Miniature taller than 34 inches, although there are Miniature Horses as tall as 38 inches.
Dwarfism has been an unfortunate outcome of selective inbreeding for size and many Miniature Horses express some clinical degree of dwarfism. Dwarfs or variations of dwarfism exhibit various degrees/combinations of conformational flaws such as dome-shaped skulls, and misshapen limbs, spines and jaws. Those mildly affected can lead normal lives whereas those more severely affected struggle to thrive.
Three major physical attributes have stubbornly refused to downsize in the Miniature Horse: the teeth, the fecal ball and the umbilical cord. Many health conditions unique to Miniature Horses can be traced back to this genetic glitch/hiccup/snag.
In the small head of a Miniature Horse we find the same number and size of teeth as found in a full-size horse. As a result, dental overcrowding, malocclusion and interrupted shedding of caps/baby teeth are quite common. Since these horses often do not wear a bit and easily maintain adequate body condition, years of abnormal dental wear can smoulder before it is recognized. Identifying and correcting dental problems in the early years is even more important in these horses.
Miniature Horses have an increased incidence of colic caused by feed impactions and obstructive fecaliths (dried hard feces) in the small colon. This type of colic is unique to Miniatures, likely due to the disparity in size between the diameter of the intestine and the fecal ball. If identified early, medical intervention may relieve the obstruction, circumventing surgery.
- More with Carol Shwetz, DVM: Vesicular stomatitis and the rules for transporting horses safely
Miniature Horses tend to have more reproductive problems than their larger cousins. The incidence of abortion/stillbirths is often more common and can be attributed to the increased rate of congenital abnormalities, malformed fetuses, or deaths due to a twisted/entangled umbilical cord. Dystocia or difficult births are also more frequent.
Predicting the date of foaling can be quite difficult in Miniatures as many do not show the classical signs of imminent birthing such as udder “bagging up” and teat waxing. It is extremely important to take special care of breeding Miniatures ensuring a rising plane of nutrition in late gestation, continuing throughout lactation.
Miniature Horses have inherited the “thrifty” gene from their pony ancestors. If measures are not undertaken to manage the body condition of the Miniature Horse, they risk metabolic derangements and founder/laminitis. Many live sedentary lifestyles further compounding their propensity towards obesity. Restricted grazing, grazing muzzles, drylots, and slow feed netting will allow these horses to move around and interact with their companions while restricting caloric intake.
Regular movement is essential for these animals. In the past many served as companion animals with little athletic expectations. However, in the last decade job descriptions of Miniature Horses have become increasingly diverse ranging from driving and agility, to becoming invaluable guide/service animals.
Obesity increases the risk for hyperlipidemia, a significant metabolic disease specific to Miniature Horses, small ponies and donkeys, whenever these animals experience a sickness or stressful episode where feed intake is interrupted for 24 hours or more a life-threatening energy “crisis” is sensed by the body. This energy “crisis” triggers fat to be mobilized from body stores where it goes to the liver to meet the demands of an energy debt. Breakdown products from fat metabolism in the liver are released into the bloodstream, causing “fatty” blood.
The problem is complicated further as the liver becomes overwhelmed with the influx of mobilized fat. Late-term pregnancy, lactation, stress, travel, weather change, illness, or any factor that impairs appetite for more than 24 hours can initiate a crisis. Affected animals will often show inappetence, lethargy, weakness, depression, neurological signs, ataxia, mild colic, tremors, diarrhea and jaundice.
Prevention of hyperlipidemia is very important because reversal of this condition is difficult in spite of aggressive veterinary intervention. Any sickness or loss of appetite in a Miniature Horse is best addressed immediately.
Clinical eclampsia is another life-threatening complication seen more commonly in Miniature Horses. It is associated with the metabolic demands of gestation and lactation when systemic calcium concentrations drop below levels necessary for sustaining electrical activity in the body. Clinical signs include muscle tremors, sweating, anxiety, bloat, colic and pupil dilation. Once again, early recognition and prompt veterinary intervention is necessary to avert death.
The colourful personalities, intelligence, and small stature of Miniature Horses have earned many of them the social status of “pet.” However, it is important to remember Miniature Horses are still a horse and/or livestock requiring similar management in many ways to their full-size counterparts. Appropriate nutrition, space to move, shelter, proper hoof and dental care, timely vaccinations and parasite control are essential to their health. It is also fundamental to educate these pint-size steeds on ground manners to ensure a healthy and safe relationship with their human companions.