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Nutritional supplements in horses
Veterinarians must show caution when recommending nutritional supplements


Nutraceuticals defined, examined

A veterinary nutraceutical is defined by the North American Veterinary Nutraceutical Council (NAVNC) as "a substance which is produced in a purified or extracted form and administered orally to patients to provide agents required for normal body structure and function and administered with the intent of improving the health and well-being of animals."7 NAVNC's mission is to promote and enhance the quality, safety and long-term effectiveness of nutraceutical use in veterinary care.

Feedstuffs have nutritive value and are generally recognized as safe, but nutraceuticals may not necessarily be. Nutraceuticals include selected nutrients, dietary supplements, functional foods, genetically engineered designer foods, hyper-nutritious foods, pharmafoods, phytochemicals (including herbs) and processed foods.

Various herbal and botanical nutraceuticals are marketed by equine supplement manufacturers for multiple purposes. Here is a brief synopsis of some of these items, their purported benefits and their noted application in horses. Although included in the list of horse products, some of these nutraceuticals have been scientifically proven only for laboratory animals or people. Regardless of the manufacturer's common claims, most of these are not AAFCO-approved feed ingredients, nor are they supported by research for use in horses.

  • Boswellia serrata: Safe use in pregnant mares hasn't been established, so it should be of concern for breeding mares. It may be a GI irritant.
  • Methylsulfonylmethane (MSM) is used to treat various illnesses in horses, including chronic muscle soreness, epiphysitis, acute laminitis, pleuritis, recurring digestive tract disorder and arthritis. While no data exist for its effectiveness, and it's intended as a source of bioavailable sulfur, studies evaluating its potential chondroprotective effect in horses haven't been reported.
  • Beta-hydroxy beta-methylbutyrate (HMB): Although HMB is used as a supplement to increase performance; prevent muscle damage after strenuous effort; increase strength, endurance, and lean muscle mass and prevent exertional rhabdomyolysis, there are little or no data to support its use in horses.
  • Devil's claw (Harpagophytum procumbens) is purported as a natural anti-inflammatory and analgesic for providing pain relief to horses and reducing inflammation in equine joints, but there are no supportive data in horses. It is contraindicated in horses with gastric and duodenal ulcers.
  • Cat's claw (Uncaria tomentosa): No studies are believed to have been performed in horses, but cat's claw purportedly fights viral infections and toxins and inhibits microorganism growth.
  • Valerian (Valeriana species): Its composition includes valerenic acids (monoterpenes, sesquiterpenes) and iridoid glycosides. Several positive benefits are claimed for horses for its sedative or tranquilizing properties because of its effects on suppressing gamma-aminobutyric acid, but no known studies have been done in horses. Valerian should not be used in conjunction with central nervous system depressants or before a horse is anesthetized.
  • Ginseng (Panax species) is commonly studied for its immunostimulatory properties. It's been shown to exert an inhibitory effect on IL-1b and IL-6 gene expression; decrease TNF-α production by macrophages; decrease COX-2 expression and suppress histamine and leukotriene release in mice and rats. As an equine supplement, ginseng is purported for stimulating the immune system, decreasing stress and increasing optimal performance, but there's no scientific literature to support its use in horses.
  • Fenugreek (Trigonella foenum-graecum) is noted as a digestive tonic, but it should not be used during pregnancy. Moreover, there is no data to support its use in horses.

Most of these nutraceuticals are not AAFCO-approved feed ingredients. No scientific literature exists that shows nutritional or other benefits in horses or supports their use in horses. Other substances in need of data to support their use in horses are outlined in Table 1.

Some of these ingredients should be prescribed with precautions. For example, some may be associated with adverse reactions to their active ingredients. Some may cause undesirable side effects or may produce effects when given with prescribed drugs. Some herbs should be of concern if fed to pregnant mares since they may stimulate the uterus (e.g., liquorice root, oregano, sage, vervain, fenugreek). Milk thistle may interfere with uptake of P450 drugs. And marshmallow root shouldn't be used simultaneously with drugs absorbed into the intestine, since it may decrease uptake.

Ed Kane, PhD, is a researcher and consultant in animal nutrition. He is an author and editor on nutrition, physiology and veterinary medicine with a background in horses, pets and livestock. Kane is based in Seattle.


1. National Research Council. The nutrient requirements of horses. 6th rev. ed. Washington, DC: National Academy of Sciences Press, 2007.

2. Guidelines for alternative and complementary veterinary medicine. J Am Vet Med Assoc 1996;209(6):1027.

3. The Dietary Supplement Health and Education Act. Congressional Rec 140:1994.

4. AAFCO Official Publication. Oxford, Ind: Association of American Feed Control Officials, 2007.

5. AAFCO Enforcement Strategy for Marketed Ingredients Working Group. AAFCO. Available at:

6. National Research Council. Safety of dietary supplements for horses, dogs, and cats. Washington, DC: National Academy of Sciences Press, 2009.

7. North American Veterinary Nutraceutical Council. Nutraceutical Council. J Equine Vet Sci 1996;16(11):486.


Source: DVM360 MAGAZINE,
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