A horse’s body uses oxygen and nutrients to produce the energy needed for basic functions, exercise, growth, and tissue repair. But this normal process also creates unstable compounds known as free radicals.
Antioxidants help maintain a healthy balance by neutralizing excess free radicals before they can damage cells. Certain nutrients also contribute to the horse’s antioxidant defense system while supporting immune function, muscle health, and recovery.
In this article, we’ll explain what antioxidants are, how they help protect horses from oxidative stress, and how to provide these essential nutrients as part of a balanced diet tailored to the individual horse.
What Are Antioxidants and Why Do Horses Need Them?
Antioxidants are compounds that help protect cells from oxidative damage.
Oxidation is a normal process that occurs as the horse’s body turns carbohydrates, fats, and proteins into energy. This process produces reactive oxygen species, commonly known as free radicals. In small amounts, free radicals support normal cell functions.
Oxidative stress occurs when the body produces more free radicals than it can control. These unstable compounds can then damage cell membranes, proteins, and other tissues.
Horses have natural antioxidant defenses, but these systems rely on nutrients supplied by the diet. Because antioxidants work together, adding one antioxidant can’t correct an otherwise deficient or unbalanced feeding program.
Some of these important nutrients include:
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Vitamin E: A fat-soluble antioxidant that helps protect cell membranes, particularly within muscle and nerve tissue
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Selenium: A trace mineral used to produce antioxidant enzymes that help neutralize damaging compounds
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Vitamin C: A water-soluble antioxidant that horses can normally produce within their bodies.
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Copper, zinc and manganese: Trace minerals needed by enzymes involved in antioxidant defense, immune function and tissue maintenance
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Beta-carotene and other compounds found in fresh plants: These contribute to the diet’s overall antioxidant capacity
How Do Antioxidants Help Protect Horses from Oxidative Stress?
Oxidative stress can increase whenever the horse’s metabolic demands rise, such as during exercise.
When the horse receives adequate antioxidants, these nutrients help protect muscle-cell membranes and support the normal processes involved in recovery.
Exercise and recovery: Adequate antioxidant intake helps protect muscle cell membranes and supports normal recovery after exercise. They do not eliminate fatigue or replace proper conditioning, hydration and rest, but they help the body manage exercise-related cellular stress.
Vitamin E: Vitamin E helps protect cell membranes from oxidative damage, especially in tissues with high oxygen demands, including skeletal muscle and nervous tissue.
Selenium: Selenium works with vitamin E by helping the body produce enzymes that protect cells from oxidative damage. Together, these nutrients support normal muscle function and recovery. However, selenium has a narrow margin between an adequate and excessive intake, so owners should avoid combining multiple selenium-containing feeds and supplements without reviewing the complete diet.
Immune function: Antioxidant nutrients also support normal immune function by helping protect healthy tissues from the reactive compounds produced during the body’s response to illness or other challenges. Balanced nutrition therefore supports both the immune response and the recovery process.
Ration Balancers: How They Can Support Antioxidant Protection in Horses
Many horses maintain their body condition easily on forage and do not need the additional calories provided by a traditional performance feed. However, forage alone may not consistently supply all the vitamins, minerals, and amino acids required for a balanced diet or to support horses with additional nutrient needs.
Ration balancers such as Tribute’s Essential K® can help provide key antioxidant nutrients without adding significant calories. This low-sugar, low-starch formula is designed for horses consuming grass hay or pasture containing 50% or less alfalfa or other legumes and supplies vitamin E, selenium, vitamin C, copper, zinc, and manganese to support antioxidant defenses, immune function, muscle health, and overall wellness.
Horses consuming diets that contain 50% or more alfalfa or other legumes may need a ration balancer formulated for legume-based forage, such as Alfa Essentials®.
Which Horses Benefit Most From Extra Antioxidant Support?
Every horse needs an adequate supply of antioxidant nutrients, but some horses may have greater nutritional demands or a higher risk of receiving an insufficient amount of antioxidants from forage alone. Some of these types of horses include:
Performance horses: Exercise increases oxygen use and free-radical production. Horses in regular training or competing often may have higher vitamin E requirements than inactive horses, particularly when they have limited access to fresh pasture. A balanced diet supports muscle function and horse recovery alongside conditioning, hydration, electrolyte replacement, and sufficient rest.
Horses with Limited Pasture Access: Fresh pasture grass, especially during certain times of the year, is one of the horse’s best natural sources of vitamin E. Horses kept primarily in stalls or dry lots and those relying on hay may receive less vitamin E than horses grazing actively growing pasture.
During transportation or competition stress: Travel, changes in routine, unfamiliar environments and repeated competition can increase the demands placed on the horse's body. Although antioxidants can't eliminate stress, adequate nutrient intake helps support normal immune function and recovery during demanding periods.
Growing horses and broodmares: Growth, pregnancy and lactation increase nutrient requirements. These horses need a feeding program designed for their life stage rather than additional antioxidants added without considering the rest of the diet.
Senior horses and horses recovering from illness: Older horses or those recovering from illness may have changing nutritional needs. Their feeding programs should be evaluated by an equine nutritionist and veterinarian, particularly when illness, weight loss, or muscle loss is present.
Can Forage and Hay Quality Affect Antioxidant Intake?
Forage should form the foundation of every horse’s diet, but its antioxidant content can vary.
Fresh, actively growing pasture is a good natural source of vitamin E. Once grass is cut and stored as hay, vitamin E levels begin to decline. Harvest conditions, heat, and storage time can cause further losses, so horses eating hay primarily may receive much less vitamin E than horses grazing fresh pasture.
Selenium levels also vary because they depend largely on the soil where the forage was grown.
A hay analysis can identify many nutritional gaps and help owners and equine nutritionists build a more balanced feeding program, although selenium may require specialized testing.
How Tribute Superior Equine Nutrition Supports Antioxidant Health, Recovery, and Performance
Tribute Superior Equine Nutrition offers fully fortified, fixed-formula feeds and ration balancers that provide key antioxidant nutrients, including vitamin E, selenium, copper, zinc, and manganese. Each ration balancer and full-intake feed is designed for specific forage types, calorie needs, workloads, and life stages to help horses receive balanced nutrition.
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Essential K®: A low-NSC ration balancer that provides essential amino acids, vitamins, and minerals without adding excess calories. It can be a good option for easy keepers, horses relying primarily on hay, or horses that need concentrated nutrient and antioxidant support without additional calories.
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Kalm ‘N EZ®: A low-sugar and starch feed that supplies controlled energy through fat and fiber. It can help support horses that need additional calories for work and recovery without excessive dietary sugar and starch.
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Senior Sport®: A highly digestible, calorie-dense feed for senior horses, hard keepers and horses that need help maintaining body condition. Its fortified nutrient profile helps support immune function, muscle health and recovery.
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Synergize®: A high-fat, high-fiber feed designed for performance horses and hard keepers with greater calorie demands. It provides balanced nutrition to support body condition and performance.
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Alfa Essentials®: A low-NSC ration balancer formulated for horses consuming forage programs that contain 50% or more alfalfa or other legumes. It provides essential nutrients without adding unnecessary calories.
Because every horse has unique nutritional needs, such as antioxidants, Tribute’s free, personalized feeding plans can help owners select a fully fortified feed or ration balancer based on forage, workload, body condition, age, and individual nutritional requirements.
References
- Deaton, C. M., Marlin, D. J., Smith, N. C., Harris, P. A., Schroter, R. C., & Kelly, F. J. (2004). Antioxidant supplementation in horses affected by recurrent airway obstruction. The Journal of Nutrition, 134(8), 2065S–2067S. https://doi.org/10.1093/jn/134.8.2065S
- O’Reilly, K., Keller, K. P., Bradbery, A. N., Hess, T., & Catalano, D. (2025). Effect of antioxidant supplementation on oxidative stress in young exercising horses [Preprint]. SSRN. https://doi.org/10.2139/ssrn.5782665
- Stucchi, L., Rossi, R., Mainardi, E., & Ferrucci, F. (2025). Antioxidant capacity and athletic condition of endurance horses undergoing nutraceutical supplementation. Journal of Equine Veterinary Science, 146, 105364. https://doi.org/10.1016/j.jevs.2025.105364
- Williams, C. A., Atherly, L. E., & Hirsch, J. D. (2007, August). Antioxidants and your horse (Fact Sheet No. 1065). Rutgers Cooperative Extension, New Jersey Agricultural Experiment Station. https://esc.rutgers.edu/fact_sheet/antioxidants-and-your-horse/
