A great deal of homework needs to be done to determine what supplements your horse may require.

Do you really know what you have in your feed room right now? Most feed rooms today contain numerous amounts of different containers, I tend to liken buying supplements to buying makeup, there are so many brands offering the same result.
Part of the appeal is that supplements offer an unparalleled level of flexibility. Your horse might by necessity be fed the same grain ration as all of the other horses on the property, but with supplements you can alter his diet for his individual needs. While your horse might benefit from a joint supplement to address his arthritis and minor aches and pains, his skinny neighbour might be putting on weight now that a supplement is helping calm his gastric ulcer. And the temperament of the mare across in  the next paddock  has mellowed thanks to a herbal preparation designed to address hormonal changes. With a formulation for virtually every problem --there's no doubt supplements are here to stay.

A Study on Supplements
In many cases there is potential to over supplement and this is very common amongst horse owners, thinking perhaps that more must be better.
Co-authors Amy Burk, PhD, of the University of Maryland, and Carey Williams, PhD, of Rutgers University in New Jersey, queried some riders entered in the 2006 and 2007 Jersey Fresh Three-Day Events about their horses' diets and found that "the majority of feeding management practices followed ... recommendations. However, the relatively high average supplement use per horse raises questions about over supplementation and/or nutrient interactions in these horses," with each horse getting an average of four different oral products, such as electrolytes, plain salt, and oral joint health supplements.
Although this survey focused specifically on eventers, it's not hard to imagine other high-performance horses might also be getting too many supplements. There's a perception among many horse owners that because supplements are over-the-counter products, they have a wide margin of safety and there is no danger in piling them on. That's true for the most part, but just because supplements aren't classified as drugs doesn't mean there is no chance of adverse reactions between competing or incompatible products.
Like any other substance your horse ingests, supplements should be treated with respect and the awareness that they have the potential to do harm, as well as good.

Be Discerning When Purchasing Supplements
Until the day when the government regulates equine supplements, it's important for horse owners to remember that oral supplements are, in large part, untested and unproven. It's important to talk to your veterinarian, do your own due diligence, and consider the horse's entire nutritional picture before you add a supplement to his diet. It's equally important to feed a supplement according to the product directions and for the length of time specified before you make up your mind as to its benefits or lack thereof. Remember that products made with inferior ingredients, quality control, or labeling might not impart any benefit, and any perceived benefit from a supplement is anecdotal evidence (not necessarily something backed up by peer-reviewed studies). The burden of confidence is definitely on the consumer when it comes to supplements, but if you select with care your horse might well reap the benefits.

What's Available

Joint health Generally these products contain glucosamine, chondroitin, hyaluronate, and/or methylsulfonylmethane (MSM), all purported to have chondroprotective (retarding degeneration of articular cartilage and promoting cartilage cell metabolism) properties. Hi Form’s ProflamAid™ formulas do not contain any of the above, they contain mineral tissue salts, vitamins, trace elements, amino acids and herbs.

Respiratory health These products are designed to help dilate bronchial passages and ease breathing for horses with allergies, small airway disease, or heaves. Garlic, ginger, elecampane, licorice root, and marshmallow (the herb) are some likely ingredients.

Anti-inflammatory and pain relief These supplements might contain herbal pain relief substitutes such as yucca, devil's claw, willow bark, or recent discoveries such as ASU (avocado and soybean unsaponifiables), which research has shown reduces the severity of cartilage breakdown and joint membrane bleeding. Hi Form formulas do not contain any of these ingredients

Antioxidant Ingredients such as vitamin C, vitamin E, selenium, and grape seed extract might help protect cells from free radical damage. Hi Form’s DeTox found in the Boutique Clinicals range contains  a range of herbs.

Calming Supplements containing valerian, chamomile, vitamin B1, L-tryptophan, and/or magnesium are used. For the hormonal swings of mares, they might contain herbs such as raspberry leaf or black cohosh. The HerbaNerve™does contain B1, L-Tryptophan, Chamomile and Mag Phos. In this formula like all Hi Form products the individual levels of nutrients are very low; the formula works synergistically for a very high effect. Dose rates are very low!

GI tract health These are designed to ease clinical signs of gastric and/or intestinal ulcers (papaya is one popular ingredient). Prebiotics are said to aid beneficial bacteria populations in the gut, and probiotics are live cultures designed to bolster the existing populations of beneficial gut bugs. Please see article on probiotics and prebiotics. The BioEquus™ is an exceptional product, whose formula has come from the human health market with very strong clinical trials behind it. It is one of the only probiotic/prebiotics available.

Electrolytes These are designed to help replace microminerals lost in sweat, usually sodium, chloride, potassium, calcium, and magnesium. Hi Form’s ElectroPlus™ is a buffered acid/alkaline formula and is highly effective.

Immune system health and Vitamins and minerals These are intended to support healthy immune system function and might contain antioxidants and/or herbal preparations such as garlic and echinacea. Hi Form’s daily supplements will assist with immune function and support the body overall by improving health and wellbeing these include the PerformPlus™, BreedPlus™ and CompletaVite™.

Energy boosters Crafted to support the efforts of performance horses, these might contain iron, vitamin B12, DMG (dimethylglycine), which could enhance muscle metabolism, and HMB (beta-hydroxy beta- methylbutyrate), which might increase lean muscle mass. Hi Form’s TopLine™ formula will assist in increasing muscle tone.
Hoof growth and health. These contain ingredients such as biotin (a B vitamin), methionine, and zinc to help grow stronger hoof horn. Using any of the daily formulas will assist with hoof growth and all contain biotin.

Senior supplements These products might address arthritic joints, decreased digestive efficiency, and tissue damage, with a variety of ingredients ranging from MSM to antioxidants to prebiotics and probiotics.

Skin and coat Products with a high fat content contribute to supple skin and a glossy hair coat. Flaxseed and other sources of omega-3 fatty acids are particularly popular. Some products might contain ingredients such as paprika to help enhance certain coat colors. Hi Form’s Equus Soy Oil ™ is an excellent source of essential fatty acids and any of the daily formulas PerformPlus™, BreedPlus™ and CompletaVite™ will assist the skin and coat.

Tendon and ligament health Silica is a possible aid in keeping tendons and ligaments elastic and resilient. Silica is also contained in the ProflamAid™ formulas.