Rocky Mountain Horse
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- 14 to 16 hands (56 to 64 inches, 142 to 163 cm)
| Other names | RMH |
|---|---|
| Country of origin | United States |
| Traits | |
| Height |
|
| Color | Any solid color allowed, but Silver dapple coloration preferred |
| Distinguishing features | Singlefoot ambling gait |
| Breed standards | |
The Rocky Mountain Horse is a horse breed developed in the state of Kentucky in the United States. Despite its name, it originated not in the Rocky Mountains, but instead in the Appalachian Mountains. A foundation stallion, brought from the western United States to eastern Kentucky around 1890, began the Rocky Mountain type in the late 19th century. In the mid-20th century, a stallion named Old Tobe, owned by a prominent breeder, was used to develop the modern type; today most Rocky Mountain Horses trace back to this stallion. In 1986, the Rocky Mountain Horse Association was formed and by 2005 has registered over 12,000 horses. The breed is known for its preferred "chocolate" coat color and flaxen mane and tail, the result of the relatively rare silver dapple gene acting on a black coat, seen in much of the population. It also exhibits a four-beat ambling gait known as the "single-foot". Originally developed as a multi-purpose riding, driving and light draft horse, today it is used mainly for trail riding and working cattle.

Rocky Mountain Horses stand between 14 and 16 hands (56 and 64 inches, 142 and 163 cm) high. Any solid color is accepted by the registry, but a dark brown color called "chocolate" with a pale, "flaxen" mane and tail is preferred.[1] This coloration is the result of the relatively rare silver dapple gene acting on a black base coat. Although uncommon, this gene has been found in over a dozen breeds, including the Rocky Mountain Horse.[2] Minimal white markings are accepted by the registry, although leg markings may not extend above the knee. The physical characteristics are somewhat variable, due to the disparate breeds that created the Rocky Mountain Horse.[1] The Rocky Mountain Horse is known by enthusiasts for its hardiness and ability to withstand winters in the mountains.[3] It is also praised for its good nature and affinity for humans.[4]
Rocky Mountain Horses have the highest risk of any breed for the genetic ocular syndrome multiple congenital ocular anomalies (MCOA), originally called equine anterior segment dysgenesis (ASD). MCOA is characterized by the abnormal development of some ocular tissues, which causes compromised vision, although generally of a mild form; the disease is non-progressive. Genetic studies from 2008 have shown that the disorder may be tied to the silver dapple gene, as most horses diagnosed with MCOA carry the gene.[5] A 2017 report by Jessica Fragola and Leandro Teixeira in Investigative Ophthalmology & Visual Science entitled "Microphthalmia with multiple ocular abnormalities in 11 horses: a novel syndrome" noted a novel ocular syndrome in horses characterized by bilateral microphthalmia and aphakia associated with multiple ocular abnormalities, and given the predominance of anterior segment lesions, a defect during the embryological development of the lens placode was suspected.[6]
The breed exhibits a natural ambling gait, called the single-foot,[7] which replaces the trot seen in a majority of horse breeds.[1] Both gaits are an intermediate speed between a walk and a canter or gallop; ambling gaits are four-beat gaits, whereas the trot is a two-beat gait. The extra footfalls provide additional smoothness to a rider because the horse always has at least one foot on the ground. This minimizes movement of the horse's topline and removes the bounce of a two-beat gait, caused by a moment of suspension followed by the jolt of two feet hitting the ground as the horse shifts from one pair of legs to the other.[8] The value of an intermediate speed is that the horse conserves energy.[9] More than thirty horse breeds are "gaited," able to perform a four-beat ambling gait, and some can also trot.[8] Thus, a Rocky Mountain Horse, with rider, can use the single-foot to cover rough ground at around 7 miles per hour (11 km/h) and short stretches of smooth ground at up to 16 miles per hour (26 km/h).[3] The faster speed is known as the rack.[7] In comparison, the average medium trot speed is 6 to 8 miles per hour (9.7 to 12.9 km/h).[10]