Supplementing Wisely

Photo: The Horse Staff

Assess your horse's overall diet, nutrient needs, health status, and workload before supplementing him.

Horse owners are passionate about their animal's diets--sometimes too passionate--and this feed-focused love can be wasteful at best and detrimental to their charges' health at worst. Over the past couple of years, researchers have published several studies proving that many owners overfeed and oversupplement their horses. For example, a group of researchers from Virginia Tech recently reported that 51% (153/300) of horses residing in a closed herd were overweight or obese. In another diet-related survey, scientists from Rutgers, The State University of New Jersey, and the University of Maryland found that top-level three-day event horses were oversupplemented, receiving an average of four nutritional supplements daily.

Because of the domestication of horses, along with modern management realities, the amount of food these animals consume is almost completely under the owner/caretaker's control. With this in mind, our goals in this article are to remind horse owners, trainers, and managers about key factors to consider when supplementing horses and to provide some tips for doing so horses wisely.

More: Greater, Additional, Further

Nowhere does the Webster's New World College Dictionary list "more" as a synonym of "better." However, many owners fall victim to the false assumption that the more vitamins and minerals they add to their horses' diets, the better.

"It is known that excessive intake of minerals can indirectly decrease the absorption of other minerals," explains Carey Williams, PhD, extension specialist and assistant director of the Equine Science Center at Rutgers. "For example, feeding a higher level of phosphorus than calcium can interfere with the absorption of calcium into bone (and an optimal calcium to phosphorus ratio is needed to promote and maintain optimal bone health and avoid skeletal problems). Therefore, horses need at least a 1:1 calcium to phosphorus ratio, and in young horses we like to increase that to a 2:1 ratio."

Oversupplemention can also result in wastage, which isn't just tough on the wallet. "Nutrient excesses, such as excessive electrolyte supplementation, are lost in urine and feces and are known to ¬negatively impact the environment," Williams notes. "Excess nitrates from protein and phosphorus in the environment that are leached into waterways can cause eutrophication (overenrichment of water with nutrients) leading to an excess growth of algae, which can kill off fish and other aquatic wildlife."

Williams has studied equine diets extensively and has proven repeatedly that many horses are indeed receiving too many supplements and nutrients. Most recently, she and colleague Amy Burk, MS, PhD, coordinator of the Equine Studies Program in the University of Maryland's Animal and Avian Sciences Department, reported that a group of upper level three-day event horses was consuming significantly higher-than-recommended daily levels of vitamin E, potassium, calcium, phosphorus, and magnesium.

"Those horses had an estimated 2.1 to five times more vitamin E per day than is recommended by the National Research Council," relays Williams. "While vitamin E itself is not toxic, excessive vitamin E, which is the most commonly supplemented antioxidant in horses ... can lower systemic beta-carotene levels, which can potentially cause a vitamin A deficiency if horses are not allowed access to fresh, green pasture."

Clinical signs of vitamin A deficiency can include night blindness, decreased immune function, and reproductive issues.

"Antioxidants like vitamins E and C are known to have many beneficial effects in exercising and older horses, but excessive levels--above 10 times the recommended level--are clearly detrimental and should be avoided," advises Williams.

Self-Control: The Ability to Exercise Restraint

According to the 2009-2010 American Horse Publication Equine Industry Survey, 80% of respondents were responsible for feeding and watering their own horses.

"One reason that horses are being overfed and oversupplemented is that owners frequently overestimate how much 'work' their horse is doing and, therefore, overestimate their nutritional demands," suggests Williams (see Table 1).

In the survey results, for instance, approximately half of the almost 11,000 respondents did not compete in 2009, indicating they used their horses primarily for recreation.


Table 1: Examples of Various Work Levels
Exercise Category Light Moderate Heavy Very Heavy
Definition 1-3 hours of exercise per week (40% walk, 50% trot, 10% canter) 3-5 hours per week (30% walk, 55% trot, 10% canter, 5% low jumping, cutting, etc.) 4-5 hours per week (20% walk, 50% trot, 15% canter, 15% gallop, jumping, etc.) Variable
Examples Recreational riding, starting a training program, some show horses School hoses, recreational riding, show horses, polo, ranch work Ranch work, polo, frequentntly showing horses, low-level eventing, race training Racing, endurance, elite three-day event horses

Pasture or good-quality hay alone can meet the nutrient requirements of horses' that aren't in heavy work or don't have special dietary needs (depending on regional deficiencies). However, Williams says many owners believe their horses' diets are not nutritionally balanced unless they are fed grain or other supplements. "This, of course, is false," she attests.

As Williams discusses in her chapters in the American Youth Horse Council's Horse Industry Handbook (2012 version), most quality hay provides all the carbohydrates, protein, fat, vitamins, and minerals a horse needs when fed with salt (sodium chloride, table salt). Yet, we as an industry currently spend more than $550 million (and counting!) on nutritional supplements for horses each year, according to data collected by the market research company Packaged Facts.

Yes, owners should avoid oversupplementing; however, keep in mind there are numerous instances when nutritional supplements might be warranted if used appropriately. Some of these include:

  • Osteoarthritis, joint disease, and joint trauma;
  • Various hoof conditions caused by a dietary imbalance (dry, brittle, cracked hooves);
  • Stress due to shipping, chronic diseases, athletic training, and competition;
  • Colic, diarrhea, or other situations where digestive support is necessary (e.g., after deworming);
  • Skin and coat ailments;
  • General illness (during which the horse might require immune support); and
  • Poor diet (e.g., if the horse's sole forage source is poor-quality hay).

If ultimately you decide your horse would benefit from one or more nutritional supplements, supplement your horse the SMART way:

Shop around Before purchasing a supplement, research which type is most likely to be safe, effective, and contain the appropriate type and amount of active ingredient. You can accomplish this quickly and easily using the ACCLAIM system.

Monitor response Unlike pharmaceutical drugs (such as corticosteroids, anti-inflammatories, pergolide for equine Cushing's disease, or thyroxine for hypothyroidism), many nutritional supplements don't have an immediate effect. Scientists have demonstrated in studies that some nutritional supplements--for example, biotin for hooves and glucosamine/chondroitin sulfate for osteoarthritis--don't cause a notable response until after a few months of consistent, daily administration. Therefore, owners/caretakers might need to be patient before deciding if a supplement is "working." At the same time, prolonged administration of a supplement with no perceivable effect (e.g., improved coat quality) could indicate the product is less than ideal and that you should pursue an alternate solution.

Avoid double-dipping It's easy for owners to oversupplement when they feed more than one product without reading labels carefully. Oversupplementing is not only potentially dangerous but also expensive. In addition, many commercially available feeds, such as concentrates, are specifically designed to meet a horse's needs, depending on his age and workload. If an owner or caretaker begins adding too many supplements, the ration's nutrition profile and nutrient balance changes, and problems due to nutrient interactions can occur.

Reevaluate your choices "Nutritional supplements can be beneficial to horses, but not all supplements are intended to be administered to all horses at all life stages," says Williams.

Electrolytes, for example, might be useful for horses that sweat daily. But if workload decreases or if the horse is exercising in cooler climates, electrolyte supplementation might no longer be necessary.

"After any change in life stage, health status, stress level, workload, or environment in general, take a look at your horse's diet and supplement schedule to assess whether any changes need to be made such as increasing or decreasing energy, forage, or supplements," says Williams.

Talk to an expert An equine nutritionist is an excellent source of information when you're assessing your horse's nutritional profile to determine if anything is missing or being fed in excess.

According to the Kentucky Equine Research report Beware of Oversupplementation, "The opinion of the veterinarian that oversees the health of your horse is a critical component of a nutritional evaluation, and that opinion can offer valuable insight into certain medical conditions that might affect nutritional status."

Talk with your veterinarian about your horse's dietary needs and work with him or her to arrange a consultation with a reputable equine nutritionist.

Danger: The State of Not Being Protected from Harm

In addition to avoiding oversupplementation, owners must consider a number of safety concerns when selecting and administering equine supplements. For example, many nutrient interactions and herb-nutrient-drug interactions have been reported in supplemented horses. The safety of the individual supplements must be measured.

Although nutritional supplements are, by definition, "generally regarded as safe," (GRAS), a designation nutritionists established in 1958, this really only means that the substance is of biologic origin and was widely consumed prior to that time. A GRAS designation does not mean the substance can't be toxic or harmful.

Heather A. Davis, DVM, of Auburn University's College of Veterinary Medicine, in Alabama, is a Clinical Pharmacology resident currently pursuing a PhD under the guidance of Dawn Boothe, DVM, PhD, Dipl. ACVIM, ACVCP. Boothe has extensive knowledge of the nutritional supplement industry and has written numerous articles describing supplements' production, regulation, and safety. She also was a key member of the National Research Council's Committee on Examining the Safety of Dietary Supplements for Horses, Dogs, and Cats.

"Supplements are not regulated the same way that drugs are by the FDA (Food and Drug Administration)," says Davis. "Therefore, when owners purchase these products ... there is no assurance that the product present in the package is the same as, or to the level of, what is being advertized by the product's label."

One of the main problems the committee identified regarding veterinary nutritional supplements was the lack of a comprehensive adverse reporting system.

"Mild adverse events, such as hives, mild diarrhea, and mild weight loss are not likely to be reported to the manufacturer, for example, but lack of adverse events being reported is weak evidence for a lack of adverse events having occurred," Davis notes.

The committee suggested structuring an adverse event reporting system to detail information regarding the dose, active ingredient, concomitant supplement administration (other supplements administered concurrently), drug or chemical exposure, and any diseases the animal might have. In addition, committee members recommended the system be publicly available.

"Dr. Boothe is developing an easy-to-use ... website for veterinarians to report adverse events," relays Davis.

At this point the best way to report an adverse supplement reaction is through your veterinarian, who can then report it to the necessary agency or organization.

Take-Home Message

Nutritional supplements are very popular, and some can be extremely beneficial. That said, ensure you supplement safely and effectively by understanding a horse's overall diet, nutrient needs, health status, and workload. Your veterinarian and an equine nutritionist play a vital role in determing your horse's needs.


About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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