Every tack shop, every feed store, every veterinarian's mobile dispensing van is virtually bulging with them these days--the buckets, tubs, and bottles of nutritional supplements available for your horse. Every horse magazine, including this one, is splashed with eye-catching ads claiming miracle results when you feed Supplement X. One promises improved hoof growth, another explosive performance benefits, and still another better lubricated joints. Some are composed of "all-natural" ingredients with soothing names like meadowsweet and fennel; others have high-tech components you can't pronounce, like polysulfated glycosaminoglycans.
It's no wonder we poor owners are a bit bewildered. With so many products available, and more appearing every day, it's almost impossible to keep up, or to sort the facts from the hype. Of course, we want the best for our horses, and many of the ads we read play on our fear that we're not supplying everything we could in their diets. If you don't feed one--or several--of these supplements, could your horse be missing out on optimum health?
What are all of these substances? Are they feeds? Drugs? Both? Neither? The answer, unfortunately, might be "all of the above."
"Nutraceuticals" is the term used most often by researchers, nutritionists, and those involved in manufacturing and marketing such supplements, which usually are designed to be administered orally. The word "nutraceutical" might be described by the dietary supplement industry as "any non-toxic food component which has demonstrated health benefits," although from a veterinary viewpoint, a more accurate description might be "a substance which is administered orally to provide agents required for normal body structure and function, and given with the intent of improving the health and well-being of the animal."
The word nutraceutical generally implies that the product is somehow derived from nature ("natural health products" is a phrase some people prefer), has a high safety threshold when ingested, and isn't designated as a drug by any of the government agencies that regulate such things.
Some nutraceuticals are vitamins and minerals that are normally included in the diet at some minor level, but when fed at a higher dosage are reputed to confer some specific benefit (the B-vitamin biotin, reputed to improve the quality of hoof horn, is an example). Others are herbal in composition, such as echinacea, garlic, and valerian. These are not necessarily natural components of a horse's diet, they are assumed to have helpful effects, based on their use in humans. Some are basically chemical. Designed to replace compounds the horse might be lacking in his own body--chondroitin sulfate, a component of healthy cartilage, is one; and gamma oryzanol, a sterol and anti-oxidant, is another.
One of the biggest problems with nutraceutical supplements is that because they exist in the zone beyond governmental control, manufacturers currently are not required to define the ingredients, and claims have to be kept pretty vague. Too specific a description of the action of the product, and the manufacturer risks it being classified as a drug, with a much more restrictive set of rules and regulations. As a result, the labels and the advertising for nutraceutical supplements often aren't much help in accurately describing the purpose and the action of the supplement, or guaranteeing you that A) the claimed dosage is what's in there, or B) an effective dosage for horses has really been determined in the first place!
Murky waters? You bet. But that's not to say that some nutraceutical supplements can't have a beneficial effect on your horse. The trouble is that for the vast majority of these products, little or no independent equine research has been done, or is likely to be done. So we're forced to rely on anecdotal evidence, extrapolations from other species (usually humans), and the reputation and accountability of the manufacturer (which varies a great deal from company to company). If enough owners, trainers, and veterinarians report a beneficial effect, a product's sales generally skyrocket, and word of mouth will spread the news. But, when you research a nutraceutical, don't believe everything you hear.
The most important caveat to keep in mind is that "natural" and "safe" are not necessarily synonyms. Just because a product originates from a plant doesn't mean it can do no harm--after all, deadly nightshade is perfectly natural, as is the incredibly toxic (but lovely) oleander bush. Most nutraceuticals have a wide safety margin, but some do have the potential to be toxic (especially when fed in doses larger than the manufacturer recommends--more is not always better!). Some might be of no benefit no matter what the dose. It's definitely a "buyer beware" market, and likely to remain so until tighter controls are instituted.
In the meantime, here's a guide to some of the more popular nutraceutical supplements currently available, and what they might (or might not) be able to do for your horse. Bear in mind that because the nutritional supplements industry is developing so rapidly, this list is far from comprehensive, but it should give you a sampling.
These are nutrients that are present in the equine diet in trace amounts, but when fed at a higher level, might have "therapeutic effects." This is the category in which there's most likely to have been some scientifically sound research on horses.
Vitamin E and selenium: Two popular additions to the diet, vitamin E and selenium are generally found as a vitamin/mineral pairing because it is thought that they work synergistically (that is, they both need to be present in the correct proportions for maximum benefit). They are known to work independently as well. Their main action is as a powerful anti-oxidant, helping to scavenge the free radicals that damage cell membranes. Vitamin E also is a player in immune function and reproductive health.
The effect of a vitamin E and selenium supplement might be improved overall health and performance, particularly for breeding stock. Performance horses on high-fat diets have a requirement for higher levels of vitamin E and selenium to help them process fats. Some researchers feel this supplement might be of benefit for horses which have a tendency to "tie up." Most horses being fed good-quality hay and a commercial grain mix already receive adequate amounts of both nutrients for good health, and aren't really in need of supplementation.
Good News/Bad News: Horses can tolerate very high levels of vitamin E without any visible adverse effects, which is one of the reasons that this vitamin is sometimes used in feeds as a natural anti-oxidant to help prevent spoilage. Selenium has a very low toxicity level in horses; there's a tiny window between "not enough" and "way too much."
Before you consider adding a vitamin E and selenium supplement to your horse's diet, you first should find out what the levels of selenium are in your local soil (most North American locations are selenium deficient, but there are a few areas where concentrations of this mineral can reach toxic levels) and in the grain you're feeding (many feeds are selenium supplemented). Definitely avoid feeding any vitamin E and selenium supplement in more than the manufacturer's recommended amounts.
Variations: Wheat germ oil is a liquid supplement that has relatively high levels of naturally occurring vitamin E; look for a product which has been "stabilized" to prevent spoilage.
Biotin: This B vitamin long has had the reputation of being able to improve the quality and growth rate of equine hoof horn. Like all B vitamins, it is manufactured by the beneficial microflora in the horse's gut in sufficient amounts for his basic metabolic needs, but some horses appear to benefit from additional biotin being supplied in the diet, at a far higher dosage than is needed strictly on a nutritional basis. (Technically, feeding a nutrient at a higher level is called hyperalimentation.)
Whether the benefits are because these horses don't absorb or utilize biotin as well as others, or whether they simply have a higher requirement, is hard to say, but the fact remains that some horses with poor-quality hooves (thin walls, shelly horn, or a slow rate of growth) appear to respond positively to biotin supplementation. There has been quite a bit of research in other species, ranging from chickens to pigs, which has demonstrated biotin's therapeutic effect on foot lesions, so it makes a certain amount of sense that this vitamin would have a similar role to play in horses' hooves. Optimum levels of biotin still have not been established for horses--it's anyone's guess what the best dosage is, but it is thought that a product should provide at least 15 mg of supplemental Biotin per day.
Variable Results: Patience is required if you're going to try a biotin supplement on your horse. Most farriers agree you won't see results for at least six to nine months, the time it takes for new horn growth to work its way down from the coronary band to the ground. Some horses, for reasons that still are poorly understood, don't seem to respond to biotin at all. Still, with the vitamin so widely available in dozens of different supplements, it's worth a try if your horse has less-than-ideal feet. Biotin, like all B vitamins, is water soluble, so it's incapable of building up to toxic levels in the body and thus is extremely safe.
Of course, biotin alone can't build better keratin (the insoluble protein that makes up most of the hoof wall). Sulfur-bearing amino acids--methionine, cystine, and cysteine-- largely are responsible for the cross-linking that helps give the material sturdiness and resiliency, and they are found in good-quality protein sources such as soybean meal. Methionine, in particular, now is included in many supplements marketed for better hoof growth because it's an essential amino acid (the horse's body can't produce it on its own).
The trace mineral zinc also has gotten a good deal of attention, but while zinc is involved in the health and integrity of hair, skin, and hooves, it's not as simple as just boosting the levels of zinc in the diet because the absorption of this mineral is linked to the dietary levels of many other trace minerals, including copper and iron. Horses tend to absorb the zinc they need in their everyday diets and discard any amount over and above that. However, since horses are pretty tolerant of this mineral, it's not likely to do any harm.
Thiamin (vitamin B1): This B vitamin long has enjoyed a reputation as a natural tranquilizer when administered in large doses either orally or in an injectable format. While it's true that injected doses of 1,000-2,000 mg of thiamin can slow the heart rate, there's little or no experimental evidence that oral doses of this vitamin have any effect on a horse's mood or performance, despite a number of studies. As a water-soluble vitamin, thiamin is fairly harmless when fed at a hyperalimentary level, but you're probably wasting your money, as it will just be excreted in the urine.
From Field And Forest
It would be almost impossible to provide a comprehensive list of all the herbs humans have fed to horses, or indeed to even catalogue all of their reputed effects--herbal supplements are a vast and ever-changing category. Many herbs do, in fact, have medicinal value, and have been noted for their therapeutic effects for thousands of years. Furthermore, many of them have documented use in horses, although the evidence might be largely anecdotal.
(In 1999, the Physicians Desk Reference for Herbal Medicines produced its first edition. Information in that book was based on renowned botanist Joerg Gruenwald, PhD, and the German Federal Authority's Commission E, "the governmental body widely recognized as having conducted the most authoritative evaluation of herbs in the world.")
It's a mistake to assume that because a product is plant-based that it's not a drug. A number of herbs, most notably valerian (the plant source of the drug valium) and willow (a source of salicylic acid, the root compound in aspirin), will in fact produce a positive drug test on urine analysis. Others with long histories of therapeutic use now have been demonstrated to be dangerous--comfrey, for example, while a valuable herb when applied topically (its leaves are used for making a poultice for intact skin bruises and sprains, for example), has been implicated in liver damage in humans and should not be taken internally. Despite this, you'll still find it as an ingredient in many herbal supplements for horses. Thus, it's important to have some background knowledge in herbs, and to read labels carefully, before you administer any herb-based supplement.
There are two main schools of study when it comes to herbs, one focusing on "Western" herbs (many originally used by Native Americans as medicinals) and the other on Chinese herbal products. Of the two, the Chinese system is the more complex, often basing its formulas on combinations of dozens of herbs, each of which is assigned a specific therapeutic effect as well as a way of interacting with other herbs. You need to undertake decades of study to really begin to understand Chinese herbology, and as a result, most equine supplements are based on the more inviting (and more readily available) Western herbs.
Buyer Beware: Because herbal supplements currently are classified as nutraceuticals, quality control can be an issue. Faced with a bucket of green dust, or compressed pellets, how is the consumer to know whether she's looking at a pure, uncontaminated source of her herb of choice, or a tub of lawn clippings? Many herbal species closely resemble other strains or species which have no medicinal value, or worse, are toxic. Unfortunately, your only protection is the reputation and accountability of the manufacturer. So, before you bring home a herbal supplement, be prepared to do your own research and ask some hard questions. Even then, don't expect startling results from a herbal product; most herbal practitioners emphasize that the action of these plants tends to be gentle and less dramatic than what you'd see with a drug.
On the theory that anything "natural" is necessarily an asset to a horse's diet, several manufacturers have promoted supplements that are based on plant or animal products, some claiming they've found the "missing link" to optimum health. While substances like kelp, blue-green algae, or bee pollen (none of which are listed in the PDR for humans) might be natural and indeed have some nutritional value, suggesting they are a "missing" part of the normal equine diet is a stretch. None of these exotic ingredients is likely to be better at supplying nutrients than the usual components of a horse's daily intake--pasture grasses, hay, and grain--and they might produce imbalances that can throw your horse's diet out of whack. (Most species of kelp, for example, have very high levels of iodine. When combined with a grain ration that also contains this mineral, the result could be iodine toxicity, or goiter.)
Better Living Through Chemistry?
At the other end of the nutraceuticals spectrum from the "all-natural" brigade are a number of supplements that seem to have leapt straight from an organic chemistry lab. These are the supplements that are most likely to bewitch and bewilder us, with their complicated explanations of their modes of action in the equine body, full of descriptions of enzymes, energy pathways, collagen matrices, and chemical precursors.
One category of high-tech nutraceuticals is focused on degenerative joint disease, or DJD, a catch-all term describing cartilage breakdown in the horse's joints that leads to arthritis and eventual lameness. Understanding the mechanism by which cartilage destruction occurs in the joints has given researchers the tools to try and reverse the process by supplying the horse with extra raw materials for healing.
Two of the injectables --sodium hyaluronate (a.k.a. hyaluronic acid) and Adequan--have yielded good results in many cases of DJD, so manufacturers have taken the next logical step and produced similar compounds that can be given orally. Such supplements have proven staggeringly popular, despite their high cost, because they're so "user-friendly," but thus far, there's surprisingly little scientific evidence supporting their effectiveness. For every study that demonstrates a beneficial result from feeding oral joint supplements, there's another showing no advantage over a placebo. That hasn't stopped consumers from shelling out vast amounts of money on the strength of anecdotal testimony.
A complete description of all of the "chondro-protective" joint supplements currently available would be an article in itself, but in brief, they're all trying to accomplish the same thing--provide the horse's body with the components that make up healthy cartilage in the hope that this will aid repair or slow down degeneration.
The cartilage matrix is made up primarily of collagen fibers, glycosaminoglycans or GAGs (which form the structural "lattice" and contribute elasticity), and sodium hyaluronate (a thick gel-type liquid that helps link the GAGs together and adds cushioning to the joints).
Chondroitin sulfate, an organic source of GAGs, is one substance that is found in many joint supplements. It's reputed to be able to increase joint fluid viscosity (and thus cut down on the grinding of bone on bone) and act as an anti-inflammatory, inhibiting some of the enzymes that escalate cartilage breakdown. Powdered shark cartilage, which contains chondroitin sulfates, is one popular way of supplying these compounds, despite it being slightly surreal to feed bits of underwater carnivore to a horse. If, like many people, you're concerned about the environmental impact of harvesting sharks for their cartilage, a more politically correct source of the same compounds is bovine tracheal cartilage, which is available from slaughterhouses in abundance.
Glucosamine hydrochloride, a component of GAGs and sodium hyaluronate, is credited with stimulating the production of GAGs in the cartilage matrix, as well as increasing the rate of utilization of chondroitin sulfate.
Which is more effective? The jury's still out on that one. One supplement (Nutramax' Cosequin) currently holds the patent on combining them; other joint supplements add bells and whistles such as manganese (a mineral that helps activate the enzymes needed to synthesize GAGs), various anti-oxidants, including vitamins A and C, or herbal anti-inflammatories such as yucca or devil's claw (which in the PDR is reported as used for "supportive therapy of degenerative disorders of the locomotor system," but should not be used in the presence of ulcers.)
Methylsulfonylmethane, more commonly known as MSM, is another chemical purported to help horses move more freely and easily. Closely related to DMSO (both are good sources of sulfur), MSM has the advantage of being a tasteless and odorless crystalline powder. It is marketed as an anti-inflammatory and seems to be particularly helpful in cases of soft tissue injury. It also has been touted for improving lung function, reducing allergic responses, enhancing circulation, helping horses cope with stress, reducing or even reversing cases of epiphysitis in foals, and bolstering the immune system. Like many other nutraceuticals, MSM has been more extensively studied in humans than in horses; the evidence suggests it has a high margin of safety, but is less clear on the specific benefits of the chemical.
Performance enhancement is tackled from another angle by the manufacturers of gamma oryzanol, a compound which seems to act as a natural, modified plant sterol (it's extracted from rice bran). Fed to horses in hard training, gamma oryzanol might increase lean muscle mass and improve strength and endurance, with fewer side-effects than steroid treatments. (Rice itself is listed in the PDR as "having been shown to be effective for pain relief and sedation of the digestive tract.")
Beta-hydroxy beta-methyl butyrate (HMB) is another compound now being marketed as a muscle builder. A metabolite of the amino acid leucine, which has been identified as being needed in greater amounts during demanding exercise, HMB has been subjected to studies with pigs, calves, and even hamsters. These showed increased lean growth, lower fat accumulations, and a good margin of safety. But the evidence it could make a racehorse run faster is still pretty sketchy.
One more compound marketed as a performance enhancer is DMG, short for N-dimethylglycine. In the body, naturally occurring quantities of DMG play an important role in cellular respiration (the exchange of gases across the cell membranes), and supplemental amounts of the chemical have been fed to Soviet (human) athletes since the 1960s. It's possible DMG might have a role in reducing lactic acid build-up in equine muscles, but its role as a "natural metabolic enhancer" might or might not translate into any noticeable performance benefit.
The Bottom Line
Is your horse really in need of any of the supplements described here (or any of the dozens we couldn't cover)? The truth is that if you're reading this magazine, you probably take your horse's health seriously, and as such, he's almost undoubtedly eating a high-quality balanced diet. Chances are very good that he gets all the nutrients he needs for optimum health from the pasture, hay, and grain you're feeding him every day, and that he'll never suffer a serious dietary deficiency. If you're interested in prevention or performance enhancement, then one or more of the supplements we've talked about might have a place in his daily regimen; but if you decide to go that route, remember that without government regulations or a requirement for a guaranteed analysis, nutraceuticals are definitely a "buyer beware" group of products. Research your choices as best you can, ask the tough questions, and don't expect miracles.
Here are some of the more common plants you might find in herbal supplements meant for horses:
Garlic--Reputed to be an "immune booster" as well as an expectorant, natural antibiotic, probiotic, and even a from-the-inside-out fly repellant, garlic has been endowed with so many beneficial properties it's almost supernatural. Of all these claims, the immune system mediating response might be the most credible, with some studies indicating a mild increase in white blood cell counts in horses fed a diet that includes garlic. Garlic has become an extremely popular feed additive in the United Kingdom, and there's increasing interest on this side of the "pond" as well. To its credit, at least we can say that garlic is inexpensive and harmless. (In the Physicians Desk Reference for Herbal Medicines, it states as effects of garlic: "The antibacterial, antimycotic, and lipid-lowering effects of garlic are proven. The drug also inhibits platelet aggregation, prolongs bleeding and clotting time, and enhances fibrinolytic activity.")
Echinacea--The purple coneflower, which might grow in your garden, is an herb that has gained a reputation for helping humans dodge colds and flu. Unfortunately, the evidence in its favor is not nearly as strong as the marketing gurus would have you believe; the latest round of studies on humans have indicated that echinacea can't reduce the rate of infection, although it might reduce the number of days you're sick. Echinacea does have a wide safety margin, however, and is generally fed to horses as an all-purpose "immune booster." (In PDR, it differentiates among four types of echinacea. It also states that, "Because of a conceivable activation of autoimmune aggressions and other overreactive immune responses, the drug should not be administered in the presence of multiple sclerosis, leukoses, collagenoses, AIDS, or tuberculosis.)
Marshmallow root--This is fabled to help soothe irritated or inflammed tissues, particularly in the respiratory tract and the gut. It's high in mucilage and might be therapeutic for horses with ulcers or chronic colic symptoms, although as usual the evidence is almost entirely anecdotal. (In the PDR, the effects are listed as "alleviates local irritation, inhibits mucociliary activity, stimulates phagocytosis, and functions as an anti-inflammatory and anti-complementary agent, immune stimulant, and hypoglycemic.")
Devil's Claw--This South African plant has anti-inflammatory and pain-killing properties that make it a common ingredient in supplements designed to assist arthritic horses. Widely used in some parts of Europe, it's reputed to have anti-spasmodic properties as well, which if true could make it a better choice than butazone for long-term gut health.
Licorice root--Its expectorant action helps loosen mucus in the respiratory tract and soothe coughs.
Dandelion--This plant has a mild diuretic action that can help reduce edema or "stocking up." Also reputed to be a "liver tonic," although the evidence for that is less clear.
Nettles--They are described as a "blood cleanser." Their action seems to be as a circulatory stimulant and to increase the volume of urine. Widely used for arthritic conditions as well as anemia (they are rich in iron, vitamin C, calcium, and potassium).
Yucca--Often used as a "bute substitute," yucca is believed to have anti-inflammatory and pain-killing properties. It's frequently recommended for arthritic conditions, although very little research has been done on its safety or effectiveness.
Apple cider vinegar--Although not strictly an herb, cider vinegar is a popular "natural" addition to the diet. Like garlic, it probably has been credited with far more healing properties than it possesses (it has been recommended for the treatment of everything from kidney infections to allergies to arthritis to skin conditions), but it is legitimately rich in potassium and several other minerals contained in apples. Generally used by pouring over the horse's grain.
Valerian--has a reputation for helping to calm nervous horses, and is widely used as a "natural tranquilizer" (it's often recommended for humans as a migraine treatment). As noted above, valerian will test positive on a drug test, so it should not be used for racing or competition horses. Also, it isn't recommended for pregnant or lactating mares.
Hawthorn--used as a "tonic" for the heart and circulatory system. Hawthorn's apparent action is to dilate peripheral blood vessels and improve circulation. It is sometimes recommended for cases of navicular and laminitis.
Black Cohosh--a nerve and muscle relaxant, this is traditionally used in the treatment of uterine disorders, and thus is found in supplements designed to soothe "mareish" mares.
Willow bark--Several different willow species contain salicylic acid, the original source of aspirin. It is used as a mild pain-killer, although eventually it might iritate the digestive tract just as aspirin does.
Manufacturers frequently combine several of these herbs in a preparation in the hopes of a "synergistic effect," which exceeds the action of any one herb on its own. While there's little or no scientific evidence that such an effect occurs, herbalists remain adamant that herbal plants work together in the body for maximum beneficial effect.--Karen Briggs
About the Author
Karen Briggs is the author of six books, including the recently updated Understanding Equine Nutrition as well as Understanding The Pony, both published by Eclipse Press. She's written a few thousand articles on subjects ranging from guttural pouch infections to how to compost your manure. She is also a Canadian certified riding coach, an equine nutritionist, and works in media relations for the harness racing industry. She lives with her band of off-the-track Thoroughbreds on a farm near Guelph, Ontario, and dabbles in eventing.
POLL: University Equine Hospitals