Equine Metabolic Syndrome / Insulin Resistance / Insulin Dysregulation

Clinical Signs

Patients with equine metabolic syndrome/insulin resistance/insulin dysregulation will often be overweight or have a tendency to be overweight. Often, the patient does not have any trouble until they have a sudden episode of laminitis.

Diagnosis

Diagnosis if often made based on a clinical syndrome or clinical “picture” based on the horse being an “easy keeper” or always having a tendency to be overweight. In some cases, we will run blood work including a resting glucose and resting insulin. This will help distinguish whether the horse is affected by insulin dysregulation.

Treatment

Treatment is primarily through dietary management and exercise. However, is some cases where elevated insulin has been confirmed, medication may be recommended to target insulin levels.

Management of Equine Metabolic Syndrome

There are several steps in dietary and daily management that are crucial in overall management of equine metabolic syndrome (EMS) and obesity. Horses that have a history of laminitis or develop laminitis will require more intense podiatry management.

Pasture Management

Horses with EMS are extremely sensitive to sugar (simple carbohydrates) and more specifically fructans. Fructans are the horse equivalent of high fructose corn syrup. Fructan content in pasture grasses varies by type of grass, length of grass, weather conditions and time of day.

Type of Grass: Cool season grasses have periods of particularly high sugar content. These include orchard grass, fescue and Kentucky bluegrass – all of which are very common in West Virginia. Sugar content in these grasses rises seasonally when we have cool nights and warm days (Think, 35-45 degree nights and 65-70 degree days of spring and fall). This is the main reason we see more episodes of laminitis during the spring and fall. In our practice, the exact timing of this critical risk period ranges from March to May and August to November, but depends on county of residence and elevation. For your own location, consider when you see frost while still having nice weather through the day.

Length of Grass: New grass has soft tender structure and more sugar compared to older, taller grass. As the grass grows it develops more lignin (fiber) which provides strength and structure. Therefore, as the grass gets taller it has proportionately less sugar in each bite (Think, tender sweet baby vegetables compared to large older vegetables that are tough and chewy). Access to pasture should be avoided in the spring when you see the young bright green grass starting to emerge. Pasture access should be restricted until the grass has reached at least 8 to 10 inches in height and the fiber content is higher.

Time of Day: Research conducted at Virginia-Maryland College of Veterinary Medicine found that fructan content in the grass changes within the same day. Fructan content is highest in the grass during the afternoon after a cool night. Based on this, we recommend avoiding grazing times in the afternoons, or turn out at night and restrict daytime grazing during the grazing season.

Fertilizer: Generally, good pasture management is great for increasing yield. Unfortunately, this is exactly what you don’t need for EMS horses. Reconsider your pasture management, you may find that you actually need to decrease treatments to reduce grazing quality.

Muzzles vs Drylot vs Timed Turnout

We encourage as much turnout as possible for mental well-being, socialization and exercise. Ultimately you will need to choose a method that works with your property and lifestyle.

Muzzles: Must be left on anytime the horse is grazing. Monitor the face for rubs and the bottom of the muzzle for being worn out and grazing hole enlargement. Muzzles often hard to keep on if there are multiple horses in the pasture as they will play and rip them off.

Drylot (or reduced pasture size): This is a more expensive but more permanent option. In some cases, just increasing the number of horses on the property to “overgraze” the pasture will be helpful. In other cases, you will need to cross fence and reduce access to a smaller area. This is convenient because it does not require a muzzle or daily maintenance but may be difficult if you have “hard keepers” and “easy keepers” in the same pasture. In our area, this seems to be the most successful long term management plan. Reducing the pasture requires an investment of fencing but requires less day to day management in the long term.

Timed Turnout: This works well in boarding stables where turnout is often limited anyway. However, it is important to note horses can eat an entire day’s worth of calories in short period of time. Therefore, if using this method, you must use a drylot or still use a muzzle to restrict intake during the turnout.

Dietary Management

Hay: Ideally, hay should be tested prior to feeding to ensure a low starch count (NSC). Hay testing can be done through Equi-Analytical. Information can be found at https://equi-analytical.com/.

However, keep in mind that hay quality may vary within the same farm and even the same field. If tested hay is not available, generally first-cutting hay will be a more appropriate choice than second-cutting hay. Just as the pasture length described above, second-cutting hay is more sugar-dense. First-cutting hay must grow longer and go to seed before it is cut, which lowers the sugar content in the stem.

Overweight Horses: Feed first-cutting hay at a rate of 2-3 % of bodyweight or 20-30 lbs per day. Use a scale to weigh the flakes of hay. Hay should be fed in a slow feeder. Slow feeders will mimic more natural feeding and help keep the horse occupied as you reduce their overall calorie intake. When introducing the slow feeder, offer the full ration as normal and then extra ration in the slow feeder. Slowly increase the portion offered in the slow feeder and decrease the portion that is free fed until eventually the entire ration is offered in the slow feeder. Gradual transition to the slow feeder will prevent stress and hunger panic from the horse as it becomes accustomed the new feeding method. There are many slow feeders available on the market and several versions that can be hand made. We recommend NibbleNets. As an alternative, you may place the hay in several piles around the lot instead of one large pile. However, this generally produces more waste than a NibbleNet or other homemade slow feeder. Caution: some horses will cause abnormal wear on their incisor teeth from chewing at nylon or metal grates on the slow feeders. This should be monitored.

Concentrate Feed (grain): Avoid feeding any grain with excessive starch such as sweet feeds or corn. Feed only a ration balancer pellet. Ration balancers offer all the benefits of much needed protein and minerals without any excess sugar. Search for a product with a minimum 28% protein content. Ration balancer pellets are readily available from many brands at many feed stores. However, many brands will refer to them by different names such as “grazing pellet, hay stretcher pellet or protein supplement” which certainly makes it difficult to choose. Locally available balancer pellets include: Enrich (PurinaMills), Empower Topline Balance (Nutrena), Essential K (Tribute), and 30% Ration Balancer (Triple Crown). Note that with any of these protein supplements, you will feed much less than with a senior feed or sweet feed. Generally, these protein supplements are designed to feed at a rate of 1-2 lbs per 1,000 lbs of bodyweight.

Supplements: There are tons of supplements marketed for both PPID and IR (or ID) horses. Most of these supplements contain chromium and/or magnesium. Research has not proven any benefit from these supplements. Therefore, we do NOT recommend any particular supplements.

Persistent Resistance to Weight Loss

If management changes have not been sufficient to induce weight loss, the overweight patient should have further testing for insulin dysregulation. Testing for a related endocrine disorder, Pituitary Pars Intermedia Dysfunction (Equine Cushing’s Disease or PPID) should be conducted. These can occur as concurrent problems or independently. If insulin abnormalities are present, additional medications, such as metformin and levothyroxine, can be prescribed for continuous or seasonal therapy to help manage the patient.

Farriery/Hoof Care

Horses with EMS (particularly obese horses) are at great risk of developing laminitis and chronic founder. Hooves should be regularly trimmed to maintain appropriate angles and a shortened toe. Special care or special shoes may be recommended for patients with discomfort from chronic laminitis. Monitor patients closely for foot abscesses. Recurring foot abscesses are a sign of micro-episodes of laminitis.

Monitoring

Horses with EMS should be continually monitored for signs of laminitis and obesity. Signs that they are not appropriately regulated include recurrent foot abscesses, laminitis, obesity, difficulty losing weight, and being an “easy keeper.”

Long-Term Management

Most horses with EMS will continue to live comfortably and have long successful careers with proper management. Many owners comment that their horses seem to be more active, more energetic and generally “feel” better once they are managed appropriately.