Antioxidants are often discussed and highlighted as being important to the equine diet. These substances are not part of any fad or the latest dietary trend. Rather, antioxidants have long been recognized by equine nutritionists worldwide as being an important consideration in the diet of the horse.

The reasoning is that antioxidants are vital to the overall health of the horse. Quite simply, they act to protect cells from damage. During times of growth, or also during times of stress, such as exercise, transport over long distances, pregnancy or lactation, the horse’s body reacts by increasing its rate of oxidation. This is because the horse is breaking down more nutrients like protein, fat, and carbohydrates to produce energy in reaction to the stress. As a by-product of this oxidation, free radicals are produced. These are also often referred to as reactive oxygen species (ROS).

Free radicals are normally produced by horses. These are molecules like hydrogen peroxide, superoxide radical, or hydroxyl radical. All are missing an electron and are considered “unstable.” Thus, as they circulate, they are damaging by seeking an additional electron to stabilize themselves by stealing electrons from cells. Under normal circumstances, free radicals do relatively little harm to the horse’s body. However, in times of stress, an overabundance of free radicals can be damaging. Free radicals are particularly damaging to muscles, skin and nerve tissue. They have also been linked to aging and even some cancers.

Antioxidants act to neutralize free radicals. They also have been linked to inhibiting free radical formation and even tissue repair. Since antioxidants can quite easily be provided by dietary sources, they have received a lot of attention by equine nutritionists. The most important antioxidants in an equine diet include:

  • Vitamin E
  • Selenium
  • Vitamin C
  • Zinc
  • Copper

Vitamin E is a fat-soluble vitamin and often considered one of the most important vitamins that horses must receive from their diet. Meaning, the horse cannot produce this vitamin internally and can only get it from their food. Thankfully for the horse, fresh forage is full of vitamin E. However, when hay is dried or cured, as most hay commonly is, it loses much of its vitamin E content.  This is one of the reasons horses that are fed only hay are recommended to have their diets supplemented with a concentrate or at minimum, given a ration balancer like Essential K®. This will ensure there is enough vitamin E in the diet to protect cellular membranes, intercellular proteins, enzymes, and other substances from oxidative damage from free radicals.

Selenium is linked with vitamin E. Together, they both act to maintain normal muscle function and protect muscles from disease. They both act to protect cells from damage by free radicals. As a trace mineral, selenium is found mainly in forage. The amount of selenium in the horse’s forage will depend on where that forage was grown. Selenium content in the soil varies greatly throughout North America. Selenium is usually higher in soils in the Rocky Mountain regions and central plains. Whereas, soils in Florida, the east coast and Pacific northwest are generally lower in selenium. Thus, like vitamin E, it is recommended that horses fed hay-only diets be supplemented with feeds or, at the very least, a ration balancer. This would also apply to grazing horses in areas where selenium is poor in the soil.

Vitamin C is a water-soluble vitamin and another important antioxidant. Vitamin C, in circulation, will stabilize any free radicals it comes across. Under normal, non-stressful conditions, vitamin C is produced in plentiful supply by the body internally. However, when stressed, there is not enough vitamin C produced to neutralize the abundance of free radicals. Therefore, an additional supply of vitamin C is recommended.

Zinc and copper are other trace minerals recognized as important nutrient sources that support a healthy immune system. Zinc and copper work together to stabilize cellular membranes and neutralize free radicals to reduce potential damage to tissues. Horses may require some supplementation of both of these minerals, especially in times of stress. It is also important they are fed in a proper 3:1 ratio. In all Tribute® products, the zinc and copper levels are properly balanced to ensure optimal absorption and function in the horse.

Overall, antioxidants are important dietary substances that are critical to the health of any horse by acting to neutralize damaging free radicals. 

If you have any questions or concerns for your own horse, we encourage you to reach out to us directly to develop a personalized feeding plan.

Chris J. Mortensen, Ph.D.