"There is a striking parallelism between humans and horses when it comes to obesity," said Philip Johnson, professor of veterinary medicine and surgery at the University of Missouri-Columbia. "Some of the very same problems humans encounter with obesity may also occur in horses."

Obesity in horses not only causes weight gain but also endocrine problems, including insulin resistance. The equine obesity risks have been less studied, but researchers believe horses have similar risks as humans, such as heart disease and diabetes.

Obesity in horses also can cause laminitis, a painful condition that often affects the front hooves. The weight of the bone is suspended in the hoof with connecting tissue forming a structure similar to a swing on a swing set. The extra weight in obese horses forces the connective tissue to tear and the bone breaks through the nail-like texture of the hooves. Veterinarians have yet to find an effective treatment for the condition. In the worst cases of laminitis, veterinarians are forced to euthanize the horse. Horses that develop insulin resistance are at an increased risk for laminitis, Johnson said.

Although society views human obesity as a harmful condition, horse owners often want their horses to look well fed. Some horse owners may view a healthy weight on their horse as too thin and try to feed them more. According to Johnson, not only do owners often over feed their horses, but what is fed to horses is genetically altered grass meant for food animals.

"The paradigm is that we feed horses the same grasses we are feeding food animals," Johnson said. "The genetically designed grass we feed horses was designed to fatten food animals quicker."

The genetics of horses, like many species, allows for the extra storing of fat in preparation for winter, when there is typically less food available. In nature, horses would eat less in the winter and lose the weight by spring. Under human care, horses are fed generously year round and never lose the extra weight.

"Horses need to be exercised daily in meaningful ways," said Johnson. "When exercising horses, owners should push their horses for a more strenuous exercise. It's not enough to ride your horse twice a week for 20 minutes."

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