Managing a horse that has equine metabolic syndrome (EMS) is challenging for a variety of reasons. These horses have increased cortisol levels and reduced insulin sensitivity which results in an inability to effectively metabolize dietary soluble carbohydrates (starches and sugars). It is common for these horses to struggle with obesity, and they have an increased risk of developing endocrinopathic laminitis as well.
A Holistic Approach
To successfully manage these horses, a holistic approach is critical. It is important to ensure that their diet is low in starch and sugar content, their calories are not oversupplied, and their nutrient requirements are being met in optimal quantities (e.g., vitamin, minerals, protein). Evaluating their exercise and housing are other important management considerations.
Part of this holistic approach to effectively manage horses with metabolic issues is the addition of supportive supplements. It is of the utmost importance to realize that a supplement will not be enough on its own to manage these horses. However, including a science-backed supplement as a part of your holistic approach can be beneficial.
There are a variety of supplements designed to provide support to EMS horses. This article will touch on some of the key ingredients that are frequently incorporated into these supplements.
Chromium
Chromium is an essential micromineral that is involved in the clearance of glucose from the blood. The potential benefit to metabolic horses is based on enhancing insulin’s ability to move glucose from the blood into the tissues. In equine supplements, chromium propionate and chromium yeast are the common forms you will see used.
A 2020 study evaluated the effects of chromium propionate supplementation on healthy Quarter Horses. The authors found that insulin sensitivity was improved when the horses were fed 2 or 4 mg daily, compared to the control horses who were receiving 0 mg. However, there was no difference seen in the horses given 8 mg daily. Unfortunately, higher levels of chromium propionate supplementation have not yet been studied.
A 2006 study with insulin-resistant ponies concluded that insulin resistance was slightly improved when chromium yeast was fed, but the insulin resistance was not resolved. Another study evaluating the supplementation of a product with chromium yeast and magnesium on ponies with a history of laminitis concluded that their insulin resistance was not improved.
More research is required before scientists can be confident in recommending an optimal feeding rate of chromium propionate or chromium yeast to metabolic horses. The science provides evidence to support chromium propionate supplementation for horses at 4 mg daily; however, it is unclear why no difference was seen in horses supplemented with 8 mg daily.
Omega-3s
Omega-3 fatty acids are popular diet inclusions for horses as they are well known for their anti-inflammatory properties. A study with mares that consumed the same diet, but had 38 g of omega-3s added from either a marine source or a plant-based source, were evaluated for insulin sensitivity. The authors concluded that insulin sensitivity improved in both treatment groups.
Resveratrol is a plant estrogen found in pistachios, grapes (and red wine!), peanuts, blueberries, cranberries, and cocoa fruit. (Marc Benedetti from Pixabay)
A 2019 study that evaluated omega-3 supplementation for EMS horses illustrated that 16 g per day of supplemental docosahexaenoic acid (DHA), a marine-derived omega-3 fatty acid, decreased the insulin response to an oral glucose test.
The science supports omega-3 supplementation for metabolic horses, but it should be noted that fat sources that provide omega-3s are often calorically dense. Therefore, if your horse is overweight, it is worth consulting with an equine nutritionist prior to adding additional fat to your easy keeper’s diet.
Resveratrol
Resveratrol is a polyphenol that has antioxidant properties and has been shown in equine research to increase antioxidant capacity. A study that evaluated a resveratrol and leucine product on insulin concentrations in EMS horses indicated that the blood insulin was lower for horses receiving the supplement, which could decrease the risk of laminitis.
Spirulina
Spirulina is a type of blue-green algae that has gained popularity as an equine supplement. It has both antioxidant and anti-inflammatory properties. Additionally, spirulina is a quality protein source for horses, which means that it provides essential amino acids.
A 2017 study with EMS horses did illustrate that spirulina supplementation was effective at improving insulin sensitivity and promoting weight loss; however, these horses were fed 500 g of spirulina daily to elicit these results. This level of supplementation can be challenging from a palatability and cost standpoint, hence more research is required to determine if lower doses of spirulina elicit similar results.
Milk thistle is showing promise for its anti-inflammatory and antioxidant effects. (Fir0002 via Wikimedia Commons)
Milk thistle
Milk thistle (Silybum marianum) may be beneficial to horses as it has both anti-inflammatory and antioxidant effects. Reducing inflammation is a key focus when discussing EMS and laminitis, which is why milk thistle may be incorporated into their diets.
Equine research has illustrated that milk thistle can increase the antioxidant capacity and may improve tissue integrity. However, a study that evaluated the safety and bioavailability in healthy horses concluded that although it was safe to feed, the bioavailability (the extent to which a substance becomes available to the body) was poor.
A 2022 study investigated the effects of milk thistle supplementation on active horses and the authors concluded that there was a positive impact on horse health, as cortisol was lower in supplemented horses. It would be beneficial to have more information on the bioavailability of milk thistle and its impact on cortisol and inflammation in EMS horses.
Take Away Message
Globally, researchers are continually working towards advancing our knowledge of equine nutrition to ensure that horse owners are equipped with information to optimally care for their horses. Understanding the science that exists in support of popular supplements is a great step towards making informed decisions for your horse. Managing horses with metabolic issues is a challenge; remember that taking a holistic approach and evaluating all aspects of their diet and management is critical.
