The harder your horse regularly exercises, the more you should consider antioxidant supplements.

Although it’s not the buzz word it was 20 years ago, antioxidants remain an extremely important part of your horse’s diet. As the name suggests, they’re substances that block reactions with oxygen, specifically, “free radical” oxygen.

Oxygen is a reactive, unstable element. The horse’s body uses it for a variety of essential functions, of course, including the destruction of invading organisms and the generation of energy from foods. However, the reactive forms of oxygen can be damaging, and these free radicals are indiscriminate about what they’ll attack and may damage health tissues and cells. Antioxidants help build the horse’s immune system to protect the body from this internal damage, as well as arming it to cope with threats caused by environmental chemicals and heavy metals.

The major antioxidant nutrients in your horse’s body are copper, zinc, manganese, selenium, the glutathione system, vitamins E, C and A, and other enzyme systems. For an example of how these interact, see the sidebar “Antioxidants At Work.”

How Much And What?
Nutritional scientists approach questions of dietary requirements by isolating a nutrient and feeding varying levels of it to see how much is needed to prevent deficiency diseases. However, another approach is simply to take a look at the natural diet. Horses eat plant material, primarily grasses, but also brush, leaves, bark etc. when grass is in short supply. 

It should come as no surprise that grasses/plants use precisely the same antioxidant defense mechanisms to protect themselves as your horse does. Specifically, live grasses and other plants contain:

• Vitamin E
• Vitamin C
• Vitamin A/beta-carotene
• Glutathione
• Glutathione reductase, SOD, peroxidases and catalases (regenerate “used” antioxidants)
• Selenoproteins (contain selenium)
• Quinones (such as coenzyme Q)
• Alpha-lipoic acid.

Put It To Use
Think seriously about antioxidant supplementation for: • Horses in regular moderate-to-heavy work. • Older horses, whose ability to keep their innate production of antioxidants up to par may be compromised by age. • Injured or ill horses. • Horses with allergies.

Some of these key nutrients must come from the horse’s diet but can be stored in the tissues against times of need. This includes minerals and fat-soluble vitamins, which the horse can’t manufacture for himself. Other nutrients­—like vitamin C, glutathione and the enzyme systems—come both from the diet and are manufactured by the horse. This combination gives the horse a safety net for surviving over the winter, in drought, etc. when the supply of live plant material may be at a premium.

In addition to the key nutrients, the horse also gets the benefit of antioxidant substances that plants produce for their own use but also work inside mammalian bodies. Some of these are:

• Bioflavonoids
• Lignin precursors
• Proanthocyanidins in legumes (same as the major antioxidant in grapeseed)
• Apigenin, Esculetin, lutein, 5,8-dihydroxycoumarin and other plant produced antioxidants

Free-roaming horses also supplement their diets with flowers, berries and seeds, all of which are particularly rich in all the antioxidants listed above, plus some others unique to fruits and seeds such as tocotrienols. These “supplement” levels are present in the basic diet of grass.

Anti-Ox, from Med-Vet/United Vet Equine, offers a comprehensive package of key ingredients.

To Supplement or Not
The major difference between horses on pasture and those stall-kept on dry diets is the level of antioxidants in their base diet. When grass it cut and cured this constitutes a major “stress” to the plant. Minerals are inert and are preserved, but antioxidants are largely destroyed during the drying and curing process.

The complexity of the antioxidant intake of a free-roaming horse makes it extremely difficult, if not impossible, to really establish the “need”/requirement for any one antioxidant. This is because the functions of antioxidants often overlap, so that if one is in short supply another may substitute. In addition, traditional deficiency-type feeding experiments only tell us how little a horse can get away with without becoming obviously ill. These studies don’t tell us what intake is optimal for health. In other words, we know horses can survive without access to fresh vegetation, but at what price to their health?

Horses maintained out on good pasture and under little stress probably don’t require antioxidant supplementation beyond correcting any mineral deficiencies or imbalances. Healthy young to middle-aged stalled or dry-lotted horses that aren’t heavily exercised or stressed also seem to do well on dry diets that at least meet their needs for trace minerals and vitamin E.

What You Need
The basics of sound antioxidant nutrition are a provision of an adequate intake of vitamin E, vitamin A and trace minerals. Trace minerals are those needed in small amounts (i.e, trace) as opposed to the major minerals, like calcium and phosphorus, which are needed in the horse’s diet in higher amounts.

Horses getting at least 1% of their body weight in hay that is a year old or less likely are getting adequate vitamin A, and all commercial feeds contain generous amounts of A. If you feed carrots, an excellent antioxidant food/treat in general, you’re also boosting beta-carotene intake, the precursor of vitamin A. So, chances are, your horse is fine for vitamin A intake.

However, since vitamin E is destroyed during the curing of hay, all horses should get at least 1500 IU of supplemental vitamin E if they are not on fresh pasture.

This leaves the trace minerals to deal with. While commercial feeds are balanced and fortified with trace minerals, hay rarely is. Zinc and/or copper deficiencies are very common, as is selenium. You can get away with less attention to trace minerals in inactive horses since manganese is rarely in short supply, and the SOD enzyme (see sidebar “Antioxidants At Work”) can use either copper or zinc. However, if your area is low or deficient in selenium, this key mineral should always be supplemented.

Therefore, the bare bones antioxidant supplementation for inactive horses on commercial grains and good quality hay is a vitamin E and selenium supplement.

Harder Work Levels
While research suggests that exercise may not greatly increase trace-mineral requirements, horses in work aren’t overly tolerant of mineral deficiencies and imbalances. Symptoms of inadequacies include muscle soreness, possibly joint/tendon problems and changes in coat color. The horse may also develop allergies or become more prone to infections as immune-system health declines. Even hoof quality may suffer.

Careful attention to trace-mineral nutritional balances and providing 150 to 200% of NRC (National Research Council) minimums of these nutrients is a wise move for all exercising horses. Blood tests to determine vitamin E and selenium status, and/or provision of extra vitamin E and selenium to these horses is also advised.

Similarly, horses battling infections, injuries and skin or respiratory allergies will benefit from careful attention to trace minerals and antioxidant vitamin intake. A case can also be made for supplementation with a few grams of vitamin C and boosting intake of other naturally occurring plant-based antioxidants. Horses with infections and allergies are the most likely to benefit by provision of plant-based antioxidants on top of very careful attention to mineral intakes and antioxidant vitamins.

Bottom Line
Your horse likely needs a good vitamin E and selenium supplement, even if he’s just at maintenance.

If he’s also an older horses or in moderate-to-heavy work he may benefit from boosting of basic antioxidant nutrients. Vita-Key’s Antioxidant Concentrate is a good choice. However, at virtually the same price, you can get the added benefit of plant-based antioxidant substances together with equivalent nutrient doses through Gateway’s Su-Per Antioxidant, which makes it our top choice.

Horses on a heavy competition schedule, shipping and facing many infectious disease challenges may also benefit from Vita-Flex’s Immusyn, as adequate glutathione production is critical both to muscular function and immune health.

For additional support in chronic inflammatory conditions and with chronic infections (e.g. Lyme), we’d have to go with Uckele’s Phyto-Quench. For respiratory allergies, try Uckele’s Bio-Quench.