Written by: Shannon Pratt-Phillips, PhD.
Careful research and sensible feeding practices are necessary to avoid over-supplementing
The equine nutritional supplement industry has a tremendous impact on the equine economy, with horse owners often spending upwards of $100/month or more on supplements for their horse. While some supplements may help improve the health or performance of your horse, some are unproven, unnecessary, and may even be dangerous. Horse owners should be encouraged to thoroughly investigate potential supplements they may use by researching their safety and efficacy based on results of scientific studies (search www.pubmed.com or even www.scholar.google.com using terms such as “equine”, “nutrition” and the compound/ ingredient you are investigating).
One of the most common types of supplements available are vitamin/mineral mixes. These nutritional supplements are intended to complement the horse’s diet to provide any vitamins or minerals that may be lacking. These supplements are particularly important for horses that may only be consuming hay or pasture which may be lacking in some of these nutrients. Forages can be an excellent source of energy, protein, some minerals (calcium, phosphorus, potassium and others) and some vitamins (particularly if it is pasture or relatively fresh hay; hay that has been stored for a while will have lower amounts of the fat soluble vitamins A, D and E). Forages will generally have low amounts of sodium, and may be low in some of the trace minerals. Thus, any horse consuming hay or pasture should be given access to salt, and ideally a trace-mineralized salt source or a vitamin/mineral supplement. Similarly, if a horse is consuming hay plus unfortified feeds such as cereal grains (oats, corn), they should be offered a vitamin/mineral mix.
If a horse is offered a commercial feed, these feeds have been fortified with sufficient vitamins and minerals to meet the needs of the intended horse, and therefore a vitamin/mineral mix is not required. Some owners do not feed the recommended amounts of the commercial feeds and therefore may also require a smaller dose of a vitamin/mineral mix offered to their horse. Alternatively, individual vitamins or minerals may be supplemented if the owner has knowledge of something specific lacking in the diet, which may be cheaper and safer than just going and offering a mixture of all of them. One of the most common causes of nutritional toxicity occurs when a horse owner feeds good quality hay, a commercial feed and then also a vitamin/mineral mix (and often horse owners may further offer specialized nutritional supplements on top of that, such as a vitamin E-selenium mix).
If a horse is at work, particularly in the hot summer months, they will be losing more of the electrolytes (Na, Cl and K) than would be found in their feed (hay and concentrate). Offering electrolytes is extremely important for such horses. A cheap alternative to commercial electrolyte mixes is to combine regular table salt (NaCl) with lite salt (KCl), although many commercial mixes include calcium and magnesium (which are also lost in sweat and therefore required in some cases) and sugar (which is not needed and large amounts can actually be detrimental).
There are several supplements available for horses that have a specific intended purpose. For example, supplements intending to improve hoof quality contain biotin, methionine and zinc, among other ingredients. Biotin is the only nutrient scientifically proven to help hoof quality in some horses; therefore, it may be more cost-effective to only offer a biotin supplement. Oral joint supplements usually contain a combination of several of the following ingredients; chondroitin sulfate, glucosamine, hyaluronic acid and methylsulfonylmethane (MSM). Some combinations of oral joint supplements have been shown to improve gait function, although in general the research is inconclusive.
Herbal supplements are fed for a variety of intended purposes, although the amount of scientific testing on such products is lacking. An excellent scientific review of the use of herbs and other functional foods can be found online (for a fee) at www.sciencedirect.com/science/article/pii/S1090023307002109.
Horse owners should learn to be critical of what they feed their horses, and not just offer their horses a supplement based on an unproven claim. Work with your veterinarian or equine nutritionist to ensure your horse’s nutrient needs are being met, and not over-supplemented.