19 Jan

Equine Dwarfism, an Undesireable Trait

Dwarf equines are mostly seen in miniature horses and miniature donkeys. Shetland ponies, Friesians, and mustangs may also give birth to dwarf horses. There are four types of dwarfism that appear in equines achondroplasia, brachiocephalic, dystrophic and hypochondrogenesis. The most apparent traits in a dwarf horse are small stature, large head, and disproportionately short limbs when compared with the body of the horse.

A dwarf miniature horse, Thumbelina, is the current Guinness World Record holder for smallest. She weighs 57 pounds and stands 17 inches high. She was born May 1, 2001, to owners Paul and Kay Goessling, in St. Louis, Missouri. She has a disproportionately large head and extremely short legs. Thumbelina has helped raise funds for various children’s charities. 

The uninformed public, often believes these traits to be appealing. Most registries will not issue a certificate for a horse with dwarf characteristics. Some horses with dwarf characteristics have slipped through registries because the traits may not be apparent in a photograph. A dwarf miniature horse or donkey may appear normal at birth. Dwarf characteristics are generally more noticeable as the horse matures.

Dwarfs have a short lifespan compared to other horses or donkeys. Equine dwarfs often battle kidney disease, pituitary or thyroid malfunctions, and other health disorders. Miniature horses without the dwarf trait are not as likely to suffer from these complexities but still, maintain the alluring small size.

Equine dwarfism occurs when a stallion and mare containing a recessive trait for the disorder are mated. The anomaly appears in all bloodlines of miniature horses. Miniature horses with successful show careers have been known to produce a dwarf colt. In order to cull dwarf equines, mares and stallions that have parented a dwarf equine must be retired from breeding. Retiring show winning miniature horses from breeding may prove costly for owners. The decision may be emotionally devastating to owners also. 

Currently, the scientific community has not developed an adequate form of testing for the recessive gene in miniature horses or donkeys that result in a dwarf equine. A DNA test was developed in 2014 to detect four of the mutations of the ACAN gene, which is known to cause dwarfism. Scientists are hopeful that in the near future, research will reveal additional information that will lead to enhanced tests.

Picture courtesy of Dwarf Horse 0028 by Mtneer Man at Flickr Creative Commons.  

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