Types of miniature dwarf horses

In the opinion of many Veterinarians, all midget horses possess some of the genetic markers for dwarfism. Equine dwarfism is a relatively rare occurrence in large horses, but it is far more common in miniature horses that have been bred exclusively for small size.

Animal research indicates that there are more than 320 separate and distinct types of dwarfism, each with a unique genetic marker and characteristics.

Unfortunately, many breeders in the horse industry categorize all congenital anomalies as a singular condition of dwarfism, and this misconception has fostered an overgeneralization regarding equine dwarfism.

Achondroplasia

Literally "shortened extremities", some types of equine achondroplastic dwarfism have specific physical characteristics such as short limbs and small ears with a normal head, neck and torso.  These deformities do not adversely affect the intelligence or lifespan of the horse.

Figure 1 - Gidget - A rescue dwarf
 

Diastrophia

Literally meaning “twisted limb”, these types of horse dwarfs are characterized by a roached-back with protruding spine, deformed leg bones, cow hocks and leg ligament anomalies. 

While diastrophic dysplasia dwarfism are characterized by severe orthopedic deficiencies and a host of other physical problems, the diastrophic dwarf can sometimes be given a quality life with expensive orthopedic surgery, corrective shoes and hoof attachments.

Figure 2 - Bluebell, a Diastrophic dwarf horse with corrective hoof attachments.

Diastrophic dwarfism is especially prevalent in USA breeding programs that attempt to quickly downsize color breeds by deliberately breeding to a dwarf stallion.  Below we see examples of this reckless breeding program for miniaturized leopard Appaloosa horses:

Figure 3 - Dottie and Spottie, Diastrophic dwarf horses with cow hocks.

Figure 4 - Coco, a Diastrophic dwarf horse, deliberate bred from a dwarf mare.

Brachiocephalia

Literally meaning “large head”, these types of horse dwarfs are characterized by small size and large domed heads. This type of dwarf may exhibit deformed limbs, severe malocclusion (monkey jaw, an "under bite with the lower teeth protruding),  and a mashed-in face, similar to a Pug dog. 

The facial issues often require corrective surgery to open-up the nostrils and prevent suffocation.

Figure 5 - Dixie, a Brachiocephalic dwarf horse after corrective surgery on nasal passages.
 

Because these traits are expressed in an almost infinite number of permutations, it is clear that all tiny horses exhibit some of the clinical degree of dwarfism and their small size is the inevitable result of decades of selective breeding for small size.

Equine dwarfism has a complete range of expression from almost-imperceptible (off-bite, short neck) to profound and crippling.  Photos of dwarf horses are published at Horsie Heaven, an online "Memorial" for owners that have lost their beloved pets. 

USA Miniature Horse is a non-profit web site dedicated to collecting useful information about miniature horses in the United States.