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Common Diseases of Miniature Horses and Small PoniesBy Kentucky Equine Research Staff · June 6, 2011

As equines, Miniatures and small ponies are subject to the same illnesses as their larger counterparts. However, some conditions are commonly seen more often in these pint-sized steeds than in large ponies and full-sized horses.

Miniature horses and donkeys are subject to a disturbance of lipid metabolism that results in abnormally high blood levels of fats and triglycerides (hyperlipemia) as well as impaired liver function. Signs are varied and may include reduced appetite, lethargy, weakness, depression, diarrhea, and edema (fluid accumulation) at the belly midline. Minis that are inappetent, inactive, obese, or insulin resistant are usually susceptible to this problem, and obese ponies experiencing some sort of stress are at increased risk. Primary hyperlipemia occurs without the presence of a predisposing disease, and this is more common in donkeys and Shetland ponies. Secondary hyperlipemia is linked to another disease process, often some sort of gastrointestinal condition, and is seen more in Miniature horses.

Treatment varies by the type of hyperlipemia and may include nutritional support, avoidance of stress, administration of heparin or insulin, and treatment of concurrent illness. Prognosis is poor for animals with primary hyperlipemia, especially if treatment is not started early in the course of disease. Aggressive treatment of the underlying disease condition can improve the health of Minis suffering from secondary hyperlipemia.

Miniature horses and small ponies are susceptible to equine Cushing's disease (ECD). This condition results from abnormalities in the pituitary gland and often leads to insulin resistance and laminitis. Ponies with ECD can be managed by eliminating grain and restricting most or all grazing. Feeding grass hay with a low carbohydrate level (less than 10% nonstructural carbohydrate) is recommended. These equines can be given a balancer pellet to supply necessary vitamins and minerals.

If it is not possible to completely remove Miniature horses from pasture, the best time for them to graze is late at night and very early in the morning when sugars are at their lowest levels in pasture grass. Use of grazing muzzles and drylots allows these horses to movearound and interact with their peers while restricting grass intake.

Minis are somewhat more likely than larger horses to have skeletal problems such as dislocation of the hip and stifle, malformation of bones in the shoulder, and osteoarthritis associated with these joints. Regular exercise and weight maintenance to limit obesity can be somewhat helpful in preventing discomfort.

Colic due to standard causes occurs in Minis with about the same frequency as in larger horses. However, in Minis under a year of age there is an increased incidence of colic caused by fecoliths (dried, hardened feces) within the small colon. Minis also have a slightly higher risk of forming abdominal adhesions after colic surgery.

An unusual problem for horses in general that is somewhat more frequent in smaller equines is collapse of the trachea (windpipe). Though this can occur in late-pregnant Miniature mares, it is more often seen in older animals and is due to tissue degeneration. Signs are extreme exercise intolerance, squeaking or wheezing sounds when the horse breathes, and an obvious effort to exhale. Prognosis is not favorable and surgery or other treatments have not been very successful.

Not a disease, but still something to keep in mind: small ponies and Miniature horses seem to have more incidences of phenylbutazone (bute) toxicity than full-sized horses. This may be related to an increased sensitivity or a misjudgment of body weight leading to an accidental overdose. Ponies and Minis being treated with bute should be monitored for gastrointestinal ulcerations and kidney disease that may result from toxicity.

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