Metabolic syndrome in horses, also known as hypothyroidism, is a relatively uncommon problem that can cause misery and suffering in your equine friend, and can drastically reduce his life span. Another term for this disease is insulin resistance, as the body does not break down the starches and carbohydrates it consumes properly. Whatever the name, the disease is a problem, and can be difficult to treat.
Metabolic syndrome in horses is a disease where the body does not use insulin as it should. Normally, when the body is flooded with carbohydrates and other foodstuffs, insulin is released into the bloodstream to regulate blood sugar levels as the energy is processed. This allows proper distribution of the fats, sugars and nutrients to the various parts of the body. In metabolic disorder, the body ignores the insulin and the nutrients flood the bloodstream, causing health issues and obesity, as the extra energy is stored as fat.
In the horse, metabolic disorder causes extreme obesity, and the animal is quite resistant to weight loss actions. Signs of metabolic disorder include fat deposits on both side of the backbone, a crested neck with fat in pads on the crest above and below the neck, and an obese stomach. In males there will be fat deposits along the sheath of the penis, and in females fat will be deposited around the anus and vulva. These animals do not cycle normally and are almost impossible to breed. They are at high risk for laminitis and most have already foundered at some point in their lives. Laminitis, also known as founder, is a devastating disease where the laminae (the blood supply of the foot) in the horse's hoof detach from the hoof wall. In the worst cases of laminitis, the coffin bone inside the hoof rotates and the hoof can actually slough off. This is a death sentence. Laminitis is one of the most feared and most difficult of equine diseases to treat.
Metabolic disorder in horses does not affect the young. In studies, the horses displaying the disorder ranged in age from 6 to 20 years; the horses were all mature and showed signs of metabolic disorder coming in. No cases were noted in horses younger than 6 years. The condition worsened with age and many horses' life spans were shortened due to recurring founder, which necessitated euthanasia.
The main treatment for metabolic disorder in horses is the reversal of the obesity of the animal. Because horses with this disease are so resistant to weight loss, all food must be removed from the animal and it placed in a "drylot" or area where there is no grazing or access to grazing. Food intake should be carefully controlled. A low-protein, high-fiber hay should be fed, and no concentrates or grains at all. Some companies are making feeds now tailored to horses with metabolic disorder, a good plan. But the best possible feed for an obese horse is low-nutrient hay. Provide all the water they want, as well as a mineral block. But reduce weight through control of feed.
If left untreated, metabolic disease will eventually claim the life of the horse. In most cases, the disease does not cause death, but the side effects will. The horse will become increasingly obese and prone to heart attacks, heaves and most dangerous--laminitis. Repeated episodes of laminitis will eventually make euthanasia a necessity.