Q: My 22-year-old gelding has been retired for the past two years due to a career-ending injury. He is pasture sound but cannot work anymore. Since I retired him, he’s gained a significant amount of weight, and my veterinarian discovered he has equine metabolic syndrome (EMS). He eats low-NSC hay and a ration balancer and wears a muzzle in the pasture. What can I do to help him lose weight without the ability to exercise him?

A: I am sorry to hear about the EMS diagnosis, but it is excellent you are doing what is best for him. Fortunately, researchers have recently taken a keen interest in EMS, providing us with solid information to assist.

Equine metabolic syndrome is an endocrine disorder that affects the horse’s body in several ways. Most commonly horses with EMS are obese with localized fat deposits, have problems regulating insulin and glucose (sometimes called insulin resistance or insulin dysregulation), and are predisposed to developing laminitis. Horses likely have a genetic predisposition to developing EMS. The thrifty gene, which helped our horses’ ancestors survive when food sources were sparce and they had to trek long distances, now makes it easy for horses to gain weight when they have limited daily exercise and access to high-quality, nutrient-dense forages and feeds. 

Managing horses with EMS comes down to preventing them from becoming overweight or obese and reducing their soluble carbohydrate intake. What you are doing so far—the low-nonstructural-carbohydrate (NSC) hay and muzzling when on pasture—are great options. To help encourage weight loss you might need to start weighing your hay and limiting your horse’s intake to 1.5% of his body weight, spread across multiple meals a day, until he gets to the desired weight. If you feed hay in a hay net, switch to one with small holes, or double-net the hay to make it harder for him to eat his hay quickly. You might also need to either eliminate his pasture access entirely or use a grazing muzzle with the smallest hole you can find to limit pasture intake. Because soluble carbohydrate levels in pasture vary throughout the day, plan your horse’s turnout for when NSC levels are lowest, usually late evening into the early morning hours. 

Exercise plays a crucial role in helping horses with EMS. Researchers have shown light to moderate exercise improves insulin sensitivity and helps horses regulate circulating glucose. If your horse can’t be ridden, develop other ways for him to get free-choice exercise. You can develop a track paddock system and space out hay, water, and shelter. This forces the horse to walk from one resource to the next like what their ancestors had to do. There are a variety of resources available on how to put these systems in place, from basic to elaborate. Regular hand-walking and groundwork can also provide your horse with low-stress exercise. 

Take-Home Message 

Managing horses with EMS involves several important considerations. What you are doing currently—feeding low-NSC hay with a ration balancer and using a muzzle—are excellent steps to help manage his weight. Restricting his pasture turnout to times when soluble carbohydrates are at their lowest and developing a track paddock system will increase his exercise and encourage weight loss without the stress of riding.

Do you have an equine nutrition question?