A Close Look at Supplement Research

When horses roamed the countryside, their diets didn't require supplementation. As horses migrated, they fed on diverse species of plants in various soils and climatic environments. Different species of plants accumulate soil minerals differently based on their physiology, soil type, and climate, and this variety probably covered all of the horse's dietary needs.

Today's horse is exposed to a fairly uniform diet, with hay or pasture lacking in diversity. Hay or pasture (forage) is the backbone of this unvaried diet, and the purpose of dietary supplementation should be to complement the diet for different situations. Different workloads, stages of growth, pregnancy, and lactation require different dietary configurations. To meet these needs, horse owners often want to use supplements. However, you should realize that supplements can cause more problems than they solve.

Combining multiple supplements without consideration for the forage might adversely affect important mineral balances. Take for example a pregnant mare fed alfalfa hay, which has a high calcium to phosphorus ratio. The owner purchases a supplement purported to be essential for pregnant mares. Pregnant mare supplements often contain high calcium levels and unnecessary calories. The combination of the alfalfa hay and the supplements in this diet could increase the risk of inducing developmental orthopedic diseases in the foal such as osteochondrosis dissecans (OCD) or possibly angular limb deformities (crooked legs), as mineral imbalance can cause abnormal bone growth. Also, excess calories make mares obese, and they then seem to have more parturition and post-foaling problems.

This problem often is compounded as more supplements are added to the diet--for improving feet, battling Cushing's disease, adding red blood cells, conditioning skin, improving appetite, etc.

Therefore, the first thing that should be done when you consider adding a supplement to any horse's diet is to determine if one is needed. You should consult with your veterinarian and equine nutritionist on this issue.

The second thing you need to realize is that supplements are not all good for your horse--and may even be harmful, as in the case of the pregnant mare above.

The third thing is that not all advertisements are completely factual. In many cases, the supplements might provide no more nutrition than a quality grain. Many supplements are not quality controlled and might not contain what the labels claim they do. There are a great many supplements with all kinds of claims that have never been substantiated with quality research. The Internet is loaded with them.

Reputable nutritionists have designed diets for pregnant mares, endurance horses, old horses, growing horses, etc. If you'd like to check out the adequacy of your horse's current diet before changing to one of these, you can ask a feed company to provide an analysis of your horse's hay (or information on hays from the area where it was grown, if available), and the company can then identify a tailored supplement that complements the forage backbone of your horse's diet.

Most of the research into dietary supplements is being performed in private industry or at universities with private industry support. Studies on disease-preventative diets are ongoing, and diets designed to prevent developmental orthopedic disease, gastric ulcers, offset conditions in geriatric horses, etc., are being evaluated.

Fat Changes Things

Joseph Pagan, PhD (Kentucky Equine Research, Versailles, Ky.) in a recent conversation summarized his point of view on this issue: "Regarding supplementation, I believe that the industry is often na�ve when developing new supplements for the equine market. There may be a much broader physiological effect than we might expect when horses are fed things that they have not evolved to eat normally. A recent research study that Kentucky Equine Research conducted in conjunction with the Waltham Center for Pet Nutrition illustrates this point.

"We have observed in a number of studies that adding fat to a grain meal dramatically reduces glycemic (blood sugar) responses after feeding, even when the actual amount of starch (complex sugars) that is fed remains con-stant. We speculated that this reduction in gly-cemic response was at least partially due to delayed gastric (stom-ach) emptying resulting from the addition of oil.

"Using a stable isotope (radiation-emitting molecule) technique, we have now determined that adding 10% vegetable oil to a grain meal doubles the length of time that the meal is retained in the horse's stomach. Whether that is a good thing or a bad thing is debatable, but the point is that vegetable oil had a major impact on GI motility that was not previously recognized.

"We as an industry really need to conduct more research on new supplements before we throw them into a pail with a fancy label and send them off for horse owners to buy."

So, be careful when considering adding supplements to your horse's diet. Consult with your veterinarian and an equine nutritionist. Over-supplementation and unbalanced supplementation is more often the problem with today's horses than dietary deficiencies.


Briggs, Karen. Nutraceutical Supplements. The Horse, February 2000, 83. Article #229 at www.TheHorse.com

Briggs, Karen. Extruded Feeds. The Horse, June 2000, 91. Article #139 at www.TheHorse.com

Briggs, Karen. Feeding The Feet. The Horse, September 2000, 87. Article #127 at www.TheHorse.com

Briggs, Karen. Joint Supplements. The Horse, November 2000, 107. Article #100 at www.TheHorse.com

Geor, Ray. Performance Boosters. The Horse, August 2000, 81. Article #162 at www.TheHorse.com

Sellnow, Les. Use and Abuse of Natural Products. The Horse, June 2000, 28. Article #148 at www.TheHorse.com

About the Author

Joseph J. Bertone, DVM, MS, Dipl. ACVS

Joseph J. Bertone, DVM, MS, Dipl. ACVS is a professor of equine medicine at Western University of Health Science's College of Veterinary Medicine in Pomona, Ca.

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