Equine Dwarfism: Not a Small Problem

These tiny horses require special management

Stories from 13th-century Norse poetry, penned by Vikings, first introduced dwarfs as mythological men with ironsmithing talents. In the following centuries, Germanic folklore described dwarfs as small yet gifted with a miraculous power to heal.

By the 19th century, the German Grimm brothers had created the popular idea of the seven dwarfs housing a runaway princess. Walt Disney later adapted that story, bringing fabled dwarfs to international pop culture at about the same time J.R.R. Tolkien started publishing fantastical tales about these creatures. These latest influences probably played the most important role in giving us the image of the fictional dwarf today. 

But in the real world of horses, dwarfism is a condition characterized by short stature and ­malformations—and, unfortunately, it doesn’t grant healing powers to go with them.

The incurable condition causes major health ­challenges, leading to a heightened risk of functional handicaps, nutritional disorders, chronic pain, and serious welfare concerns. With good knowledge about dwarfism in horses, combined with a financial and moral commitment to their care, however, we can help dwarf Miniature Horses lead lives that are as healthy and comfortable as possible.

Dwarfs: The Good and The Bad

Technically speaking, “dwarfism” can be a breeding goal or a breeding nightmare, says John Eberth, MS, a PhD candidate at the University of Kentucky’s Gluck Equine Research Center, in Lexington. It all depends on the kind of dwarfism.

Scientists categorize dwarfism as being either proportional or disproportional, Eberth says. Proportional dwarfism is exactly like it sounds: Everything is smaller. With disproportional dwarfism, however, only some of the body parts are smaller, putting the individual visibly out of proportion.

“You could have a normal-sized head and body but short limbs, for example,” he says.

Proportional dwarfism has brought us the true “miniature” breeds of animals of different species—Miniature Schnauzers, Miniature Goats, and, of course, Miniature Horses, among others. These animals are usually healthy and carry normal genes for proportionally dwarfed individuals.

Disproportional dwarfism creates animals that can face sometimes-severe health issues, due mostly to their disproportionate body. Worse, because dwarfism is hereditary, a breeder could end up with an entire herd of unhealthy animals. “The goal is to remove these disproportionate dwarf genes from breeding programs entirely,” Eberth says.

Equine Dwarfism: Not a Small Problem

Squeezing Everything in There

Genetic mutations cause disproportional equine dwarfs to have short, stocky, skeletons (see TheHorse.com/166155 for the details on dwarf DNA). But those mutations have no effect on organ ­development.

Practically speaking, this means things don’t fit. “You’ve got this tiny, misshapen hard tissue structure, and you’re trying to pack all these normal-sized soft tissues into it,” Eberth says. “It just doesn’t work.”

The situation is not only painful—and increasingly so as the Mini gets older—but also disruptive to proper organ function. Plus, those organs still demand “normal” nutrition, says Liz J. Barrett, DVM, MS, Dipl. ACVS, associate veterinarian at Hagyard Equine Medical Institute, in Lexington, Kentucky. She treats the dwarfs at The Peeps Foundation, which specializing in the rescue, rehabilitation, and care of dwarf Minis in Lexington and in Wellington, Florida. “The dwarf is a smaller size, but his internal organs still require the same amount of nutrients as a bigger animal,” she says.

Unfortunately, though, those organs don’t always get what they need—either because the owners misunderstand nutritional needs or because the organs “outgrow” their frame.

“The disease itself doesn’t kill the dwarf as he ages; it’s the complications that kill him,” says Eberth. “Dwarfism can kill by starvation or colic, due to the internal organs being restricted in size and those smaller skeletal structures just compacting the internal organs that are the same size as if the horse were (a) full-grown (nondwarf Miniature Horse).”

Locked Jaws, Roach Backs, and Other Secondary Effects

When bone growth gets stunted, the entire skeletal system becomes bulky, twists, and deforms. You commonly see this affect dwarfs’ jaws, says Eberth. The teeth start out normal, but as the jaw grows abnormally, they become poorly aligned.

“They often get an underbite, and the front teeth don’t wear anymore and just keep growing,” he says. “Then the molars get out of alignment, and they develop hooks. They literally can’t grind or chew.”

Meanwhile, the joints become restricted to the point that the jaw locks up. “They need a lot of dental maintenance, up to four times a year or more,” Eberth adds.

The horses’ vertebrae become misshapen during the ossification (bone development) process. This is complicated by the fact that the spine is supporting a disproportionate body, resulting in poor spinal alignment. “The only way they can deal with these abnormalities is by forming a roach back (up-curving spine),” says Eberth. The roach back sets off a domino effect of musculoskeletal issues, including hip dysplasia, hip rotation, goose rump, and sickle hocks.

The humped back, plus the nature of the disease itself, leads to a host of other problems, says Barrett. “We see orthopedic issues, a lot of angular limb deformities, flexural limb deformities, and arthritis,” she says. Arthritis can occur in dwarfs as young as a year old due to uneven weight-bearing on the joints.

While she’s performed surgery on some of the dwarfs at The Peeps Foundation to correct orthopedic issues, she says she’s found that conservative treatment with corrective shoeing or braces is better—mainly because these little guys don’t handle anesthesia well. “They don’t seem to have a normal metabolic status for some reason and can run into liver issues with all the drugs,” she says. “Plus, they’re just very small—much smaller than most humans—so dosing is critical.”

Their size and proportions might also make them more likely to pick up respiratory diseases, she adds. “The dwarfs seem to be the ones that are more likely to have a snotty nose,” she says. “I don’t know if it’s something to do with their immune system or if it’s just that everything is smaller and it’s harder to clear things.”

Dwarf Minis also tend to have cardiac issues, says Josh Dolan, co-founder of The Peeps Foundation. “I have 25 dwarfs right now, and every single one has a heart murmur,” he says.

As they become more malformed and develop greater pain and loss of movement, these horses become more sedentary, says Eberth. This inactivity interferes with digestion and general musculoskeletal health, and it has severe consequences on the welfare of an animal that’s evolved to move almost constantly. “With combined digestive, musculoskeletal, and hoof issues, these dwarfs get into a snowball effect, and there’s just no stopping it once it’s started,” he says.

Life expectancy in equine dwarfs varies considerably, depending on the extent of the malformation and the care. “Some die in the first year; others can live up to 15 years,” says Eberth.

The Dwarf Diet

As we know, feeding the dwarf can be a challenge due to having the nutritional needs of a full-sized Mini compacted into a tiny frame. There’s also the issue of these horses’ jaw and dental problems.

“Some of them can end up with a mash or liquid diet, but these animals can secondarily starve to death because they’re not getting enough nutrients to survive,” Eberth says. “These individuals are often very thin and have a lot of gastrointestinal tract issues.”

Though many appear to be “fat,” it’s important to remember that the big belly comes from bulging organs, not obesity. “We feed ours an amazing amount of food,” Dolan says. “It’s surprising how much they need to eat.” 

And for those frequent dental-care visits, they need skilled dental professionals, adds Barrett. “It’s not always easy because they’re so small,” she says, adding that not all practitioners have the appropriate equipment.

Equine Dwarfism: Not a Small Problem

Miserable Little Feet

Dwarf feet are true victims of their cartilage protein-affecting mutation, says Eberth. Like the organs, the hooves themselves start out healthy and normal. While they’re not compacted by a skeleton, they’re still linked to the bony structure inside the foot. And as the foal grows, the bone wreaks havoc on the surrounding tissues.

“The coffin bone (which is within the hoof capsule) becomes malformed, the joints fuse, the limb bones grow abnormally, and all that puts all the angles out of alignment,” Eberth says.

Indeed, along the whole length of the leg, all the way down to the pointed coffin bone, dysfunctional bone growth has serious repercussions in the hooves. The growing feet try to compensate for misalignment and asymmetries of the abnormally shaped bones within. “They curve and hook and twist and grow sideways and develop club feet … It’s a mess,” Eberth says.

Interestingly, he adds, these dwarfs rarely have laminitis. “It can look like laminitis, and people sometimes confuse it for laminitis,” he says. “But it is the disease progression of the limb deformities in the dwarf Miniatures restricting movement and causing pain.”

Dolan says good corrective shoeing works wonders for these little feet. “We use polyurethane shoes that we glue on to the front of the hoof,” he says. “And we often use an extensor that allows them to have a lot of support, and this strengthens their ligaments in a healthy way and makes them more comfortable.”

Managing the feet correctly from the beginning helps keep things straight and supported as the dwarf grows. “It’s a lot harder to fix once the joints close up and the tendons (finish developing),” he says, which occurs by the time they’re 2.

Responsible Breeding

Again, they’re adorable and cuddly, but that’s no reason to aim for one. “Back in the ’80s, some breeders of Minis thought these were the ideal Mini and started selecting for them, without understanding their pathology (disease),” Eberth says. “Dwarfism skyrocketed, with detrimental effects on the breed.”

The mutations are recessive, but the odds of it manifesting are still fairly high. “If you breed two healthy carriers of a dwarf mutation, you’ll have a 25% chance that the offspring is a dwarf,” he says.

Fortunately, genetic testing now exists. “You can safely breed a carrier to a noncarrier and not have a chance of producing a dwarf,” Eberth says. “So you don’t have to scrap your breeding program. You just need to make wise and informed decisions. Educate yourself as much as you can—about the disease and about your own breeding stock.”

Take-Home Message

Unlike the magical creatures of fantasy in German fables, Miniature Horse dwarfs do not have special powers—aside from stealing people’s hearts. They’re precious, but these animals’ genetic condition puts them at a high risk of health and welfare issues, and their care is both time-consuming and expensive (“We’re talking thousands and thousands of dollars per year,” Eberth says).

While researchers are still uncovering the extent of these equids’ health problems, current goals are to treat existing dwarfs as early as possible and to prevent the birth of new dwarfs through genetic testing and responsible breeding.