What’s in an Equine Supplement?

Here’s what current research, or lack thereof, is telling us about common equine supplement ingredients.
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There is evidence that some supplement ingredients can improve osteoarthritis, gastric ulcers, and inflammation and increase insulin sensitivity. | Photo: iStock

Here’s what current research, or lack thereof, is telling us about common equine supplement ingredients.

From vitamins and minerals to fats and yeast cultures, horse owners face hundreds of choices when deciding which, if any, nutritional supplements their horses need added to their daily feed. What really works, and what’s just the latest dietary fad?   

In contrast to drugs, top-dressed supplements or those provided free-choice to improve nutrition or performance are regulated in a way that does not require research proving their efficacy and safety. But as with any bagged feed product, supplement labels must include the product’s purpose statement, ingredients, guaranteed analysis of nutrients provided, and directions for use. To help horse owners with their supplement decision-making process, we’ve taken a look at what scientists have discovered recently regarding common ingredients’ usefulness.

Joint Supplements

We’ll start with the particularly prevalent chondroprotectives (designed to support articular, or joint, cartilage and synovial fluid), which owners pursue on good principle: Joint health, and preventing and alleviating osteoarthritis, are vital to maximizing our equine athletes’ performance and our geriatrics’ longevity. To date, typical chondroprotective ingredients have included glucosamine (hydrochloride or sulfate) and/or chondroitin sulfate (CS), an endogenous (naturally occurring) component of normal equine articular cartilage. Manufacturers commonly provide glucosamine and chondroitin sulfate (GC) together, as researchers have implicated the combination is more effective than each part given alone.

Here are a few significant recent research findings regarding these joint supplement ingredients and others:

  • In equine in vitro studies (in the lab), including one conducted at Michigan State University, researchers have investigated GC’s role in repairing joints after trauma from injury or repeated stress. When they added GC to a nutrient mixture, stress indicators in cartilage reduced significantly to levels similar to those found in healthy cartilage.  
  • In a recent study out of the University of Georgia, researchers observed that oral glucosamine sulfate improved sound, aged horses’ gaits.  
  • In trying to find a way to test oral GC’s efficacy, nutritionists at Texas A&M University did not detect glucosamine (which, again, is present in horses normally) in either control or oral GC-supplemented horses’ plasma. They did find similar chondroitin sulfate levels among the control and GC groups, suggesting that GC might be altered in the digestive tract and CS wasn’t “joining” that already present in the body.     
  • In 2009 Manhart et al. discovered that polyunsaturated fatty acid (PUFA) supplementation helped reduce joint inflammation markers in arthritic horses. They used the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are found in high concentrations in cold-water fish oils. But in a similar study in 2011, in which Ross et al. used mature, healthy horses, fish oil did not reduce joint inflammation.  
  • Other ingredients, such as green-lipped mussel tissue and hyaluronic acid, might potentially reduce the effects of osteoarthritis, but limited research is available to support this. To date, there is little data suggesting methylsulfonylmethane (MSM) is an effective joint supplement, although many manufacturers commonly incorporate it in their equine chondroprotective supplements.

The Omegas

Horses cannot synthesize the essential PUFAs linoleic and α-linolenic acid, which play a vital role in functions including immunity, cellular membrane integrity, and nervous system function. Therefore, horses must rely on other sources, such as supplements, to extrapolate their benefits. Vegetable oils, including soy and corn oil, are high in omega-6 fatty acids and commonly used as a highly palatable calorie source. Documented benefits of added vegetable fat include decreased glycemic (glucose) and insulinemic response in the blood, decreased excitability and nervousness, and lower weaning stress.  

Nutritionists have not yet established a suggested omega-6 to omega-3 ratio, but equine diets tend toward greater omega-6 concentrations than omega-3. They’ve noted benefits to supplementing to increase a horse’s omega-3 levels, including the reduced inflammatory markers and reduced osteoarthritis described, and lower exercising heart rates. The most common ingredient in omega-3 supplements is flaxseed, but evidence is beginning to unveil the importance of EPA and DHA found in fish oils. Recently, researchers at Tarleton State University, in Texas, found that fish oil supplementation increased EPA and DHA in synovial fluid, red blood cells, plasma, and skeletal muscle, while added flaxseed did not.  

Trinette Jones, PhD, assistant professor in animal sciences at Tarleton, suggests EPA/DHAs real value as anti-inflammatory agents might be in how they resolve inflammation rather than how they prevent it. When selecting an omega-3 supplement, Jones says, “It needs to be high in EPA and DHA and have more EPA than DHA, as EPA appears to have the more anti-inflammatory effects.”

Digestive Supplements

Digestive disturbances, such as colic and gastric ulcers, affect many performance horses. Owners frequently turn to medicinal management, but recent advances in nutritional additives might support these horses as well.

Digestive supplements commonly contain prebiotics and probiotics. Prebiotics are substances that nutritionally support the hindgut’s bacteria population and typically include oligosaccharides and yeast products. Most researchers have concentrated on prebiotics’ ability to improve nutrient digestion, immune function, and intestinal disturbances. Yeast cultures most consistently improve horses’ protein digestibility. Scientists have yet to determine if oligosaccharides have a positive effect on immune function, except in young, growing horses where prebiotics have been shown to decrease the incidence of foal diarrhea.

Probiotics, a source of live, naturally occurring microorganisms, provide species commonly present in the large intestine. Probiotics potentially can prevent pathogenic bacteria from colonizing in the gut. Research results suggest that the live bacteria will survive passage through a horse’s digestive system, although their potential benefit has not yet been determined.

Little has been published on herbal, berry, and other nontraditional ingredients’ efficacy, except within the gastric support category. In an in vitro study using a red marine algae-based supplement, researchers observed the algae were capable of buffering acidic conditions similar to those of the equine stomach within varying grain and fiber environments. Louisiana State University researchers found that horses fed sea buckthorn berries and pulp for 28 days prior to feed deprivation developed fewer and less severe gastric ulcers in the stomach’s glandular region (lined with thick, bumpy glands that both protect the stomach lining and produce digestive acids) than controls, but they saw no differences in the nonglandular region (the upper, unprotected part of the stomach) where ulcers are most common. In a study where horses consumed sea buckthorn berry supplements for 67 days, ulcer scores stayed the same or decreased in 87% of the treated horses versus 25% of the controls.  

Most digestive supplements include blends of prebiotics, probiotics, buffering agents, antioxidants, and herbs. Frank Andrews, DVM, MS, Dipl. ACVIM, professor of veterinary medicine at Louisiana State University’s School of Veterinary Medicine, has shown that the key ingredients for stomach health include fruit pectin, lecithin, and sea buckthorn berries and pulp. “Pectin and lecithin act as barriers for the gastric mucosal membranes against excess gastric acid,” he says. “Lecithin and sea buckthorn berries contain natural antioxidant properties that protect the stomach lining from release of oxygen free radicals and resulting tissue breakdown and inflammation.”  

Metabolic Support

A recent supplement trend has been to support horses with equine metabolic syndrome, insulin resistance (IR), and/or laminitis. Extrapolating from human studies, scientists hypothesize that these horses might benefit from additives such as chromium, magnesium, cinnamon, psyllium, and omega-3 fatty acids.

In diabetic human patients, omega-3 fatty acid supplementation improved insulin sensitivity (insulin’s ability to signal glucose to move from the blood to storage in muscle, liver, etc.). Rats and pigs had similar improvements after supplementation with EPA and DHA from fish oil.  

Fish oil and flaxseed tended to improve insulin sensitivity in IR horses, but not in normal horses. Conversely, in a 2012 study by Hess et al., fish oil did not impact insulin sensitivity of either IR or non-IR mares. Nutritionists hypothesize that fish oil’s anti-inflammatory properties might reduce laminar inflammation during laminitis, but research into this does not exist.

Chromium and magnesium have been shown to improve insulin sensitivity in humans, but not in horses. Similarly, cinnamon has been shown to improve insulin sensitivity in humans and rats, but it did not affect insulin sensitivity in mares.

Recently, Montana State University researchers found that 60 days of psyllium (a plant-derived substance) supplementation lowered blood glucose and insulin levels after a meal in normal, nonobese horses. Also, when horses were allowed to graze on rapidly growing cool-season grasses, those supplemented with 180 g of psyllium had lower blood glucose and insulin levels. The same results have yet to be confirmed in horses with metabolic conditions.

Other Common Supplements

While recent research has been focused elsewhere, supplements for hoof, skin, coat, behavior, and performance, among others, remain popular. Here are some more examples of common ingredients:

  • Owners often administer biotin to improve hoof quality, and study results have indicated that biotin might improve hoof growth and strength.
  • Researchers know that adequate levels of essential fatty acids can help improve skin and coat quality. There has been evidence that omega-3 fatty acids from flaxseed can reduce the skin’s reaction to seasonal pruritis (itching).
  • Little or no evidence exists to support the use of herbs, such as chamomile, or amino acids, such as tryptophan, for nervousness or anxiety, although these often appear in behavioral supplements.  
  • Electrolytes have scientific backing for improving hydration status, reducing muscle fatigue, and increasing endurance by replenishing sodium, potassium, and chloride lost in sweat during exercise. In 2013 researchers from the University of Guelph found that a scientifically balanced powdered blend of sodium, potassium, and chloride was rapidly absorbed and distributed to the body. Also, horses that consumed an electrolyte supplement were able to complete submaximal exercise (e.g., endurance racing) for longer durations.

Take-Home Message

There is evidence that some supplement ingredients can improve osteoarthritis, gastric ulcers, and inflammation and increase insulin sensitivity. However, meeting a horse’s daily nutrient requirements and providing adequate forage and veterinary care need to be the primary emphasis for equine health before you supplement.


Written by:

Kristen M. Janicki, a lifelong horsewoman, was born and raised in the suburbs of Chicago. She received her Bachelor of Science degree in Animal Sciences from the University of Illinois at Urbana-Champaign and later attended graduate school at the University of Kentucky, studying under Dr. Laurie Lawrence in the area of Equine Nutrition. Kristen has been a performance horse nutritionist for an industry feed manufacturer for more than a decade. Her job entails evaluating and improving the performance of the sport horse through proper nutrition.

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