Antioxidants are important nutrients for horses that help to combat oxidative stress, maintain overall health, and support performance. They work by neutralizing harmful molecules known as free radicals within the body.

Free radicals are highly reactive molecules with an electrical charge that are produced in the horse’s body during normal metabolic processes. These molecules can accumulate and cause damage to cellular structures in their search to become stable, leading to a range of health issues. This damage is often referred to as oxidative stress (oxidation).

In horses, stressful conditions such as intense exercise, traveling long distances, illness, pregnancy, and advanced age are associated with increased oxidative stress and reduced antioxidant status. Over time, oxidation can contribute to muscle fatigue, impaired performance, inflammation, and chronic disease. [1]

Horses obtain antioxidants naturally through their diet and synthesize some of them in their body. [2] However, in some cases feeding supplemental antioxidants can be beneficial to combat free radicals and safeguard your horse against oxidative stress.

Common antioxidants in the equine diet include vitamins C and E, selenium, zinc, and copper. Other antioxidant supplements that are frequently fed to horses include alpha-lipoic acid, coenzyme Q-10, docosahexaenoic acid (DHA) and acetyl-l-carnitine (ALCAR).

What is an Antioxidant?

Antioxidants are molecules that counteract the damaging effects of highly reactive compounds known as free radicals by neutralizing their electrical charge. Like all living organisms, horses constantly produce free radicals as natural byproducts of metabolic processes. Exposure to heavy metals and environmental toxins also results in oxidative stress. [19]

If left unchecked, these free radical molecules can cause cellular damage to tissues and organs by stealing electrons from other molecules, a process known as oxidation.

Oxidation can affect various molecules within cells, such as DNA, proteins, and lipids in cell membranes. The mitochondria, where cellular energy (ATP) is generated in the presence of oxygen, are particularly vulnerable because of a high concentration of free electrons.

When molecules in cellular structures are oxidized, their functions can be compromised, which can ultimately impact the health of the organism, leading to inflammation, aging, and various diseases.

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Causes of Oxidative Stress

In horses, as in all mammals, oxidation naturally occurs as a result of metabolic processes. Free radicals are naturally produced when nutrients are broken down from the diet to generate energy. [1]

Free radicals do play some important roles in the body, including aiding the immune system in defending against foreign invaders and supporting the adaptive response to exercise. However, an overabundance of these molecules can be detrimental.

However, excessive levels of circulating free radicals are harmful as they can cause damage to muscle, nerve, and skin tissues and promote cell death by destroying cell proteins, DNA, and fatty acids.

Oxidative stress occurs when there’s an imbalance between the production of free radicals and the body’s ability to neutralize them. Oxidative damage is more likely during periods of growth, stress or exertion when the body rapidly breaks down nutrients including protein, carbohydrates, and fat to produce energy. [1]

Oxidative stress is also elevated under the following conditions:

  • Heavy Work: Intense or prolonged exercise can increase the production of free radicals. This is particularly evident in athletes like racehorses after strenuous workouts or competition.
  • Pregnancy and Lactation: Pregnant and lactating broodmares have increased energy demands, resulting in a faster metabolism and increased free radical generation.
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