Equine Metabolic Syndrome
Equine Metabolic Syndrome
January 25, 2023 | News and Publications | The American Quarter Horse Journal , Healthcare and medication , Feeding , Horse Health and care
By Dr. Thomas Lenz
Equine metabolic syndrome is also referred to as peripheral Cushing's syndrome because horses with the condition exhibit symptoms that are similar to those exhibited by horses suffering from Cushing's disease. The difference is that horses with metabolic syndrome can be relatively young and have no abnormalities in their pituitary or adrenal glands. In addition, unlike Cushing's disease, which usually affects geriatric horses, metabolic syndrome horses tend to be between the ages of 8 and 20 and are always overweight, with large fat deposits in the crest of the neck, over their croup and in their abdomen.
What Causes Metabolic Syndrome in Horses
Scientists have recently discovered the root of the problem is the omental adipose cells (far cells in the horse's abdomen) that not only score fat but actually produce hormones similar to those produced by the adrenal glands. These hormones are thought to cause insulin resistance that prevents the horse's body from using and metabolizing glucose properly.
Insulin normally is secreted by cells in the pancreas in response to glucose in the horse's bloodstream after a meal. Insulin stimulates uptake of glucose by the liver, muscles and fat and decreases its levels in the blood. It also decreases the production of glucose by the liver. In insulin-resistant horses, the insulin doesn't work at the cellular level, resulting in excess free glucose in the blood that is distributed to cells that don't need it. High levels of unregulated blood glucose in the horse are a concern because it can be toxic to the cells that line the horse's blood vessels, especially those in the feet.
This result is often damage to the sensitive laminae of the horse's feet and the development of clinical laminitis (founder).
Signs of Equine Metabolic Syndrome
Clinical or subclinical laminitis is a common problem in these horses, especially in the spring when pastures are lush. Where laminitis is not evident, there are often distinct changes in the horse's hooves, such as laminitic rings or widening of the white line that suggests laminitis has occurred, despite the absence of apparent previous clinical signs of foot pain.
There is no definitive diagnostic test for metabolic syndrome. Because there is not a problem with the horse's pituitary gland-adrenal axis, the tests we commonly use to diagnose true Cushing's disease turn up normal. However, resting blood insulin levels can be measured.
Treatment for Metabolic Syndrome in Horses
There are several ways to treat and/or manage horses with suspected metabolic syndrome. Undoubtedly the most effective is to undertake a gradual program of conditioning and weight loss. Getting your horses in shape and getting rid of excess fat will reduce the amount of fat in their abdomens and their hormone production. When feeding affected horses, avoid starchy, high-glycemic-index feeds such as corn, oats, barley and molasses. Reduce the amount and time horses spend on lush, new grass. If you are unable to remove horses completely from pasture, grazing muzzles are a great way to slow down grass intake. Feeds that are beneficial and should be fed to affected horses include most grass hays, beet pulp and soy hulls. If your hay is of extremely good quality, you may want to soak it in water to reduce the sugar content.
We have all known for years that there are those horses that are "good doers" and tend to founder easily, especially in the spring on lush, green grass.
Now, thanks to research, we know that these horses are actually suffering from a metabolic disease that once recognized can be managed through proper nutrition and plenty of exercise.
Dr. Thomas Lenz is a former columnist for The American Quarter Horse Journal and is a member of the American Quarter Horse Hall of Fame.