Q. I’ve heard that vitamin E is important for the equine immune system. My horse travels quite a bit for competitions, so I’m always interested in supporting his immune health. Can you explain why exactly vitamin E is important for their immune health? And should I consider giving my horse a vitamin E supplement if he’s not getting adequate amounts from his forage?
— Lucy C., Michigan
A. Vitamin E, a fat-soluble antioxidant, plays a crucial role in maintaining the health of horses, particularly in supporting their immune systems. It’s an essential nutrient that horses cannot synthesize on their own, and it must be obtained from their diet, primarily through fresh forage.
Vitamin E plays supports the immune system of horses by protecting immune cells from oxidative stress, enhancing phagocytosis, boosting antibody production and reducing inflammation. Given its importance, ensuring adequate vitamin E intake through diet or supplementation in equine diets is a priority for owners, trainers and veterinarians alike, especially considering its profound impact on the immune system, muscle function and overall vitality of the horse.
A proactive approach to vitamin E nutrition can make a significant difference in a horse’s ability to resist disease, recover from injury and maintain optimal health and can be especially beneficial for those under stress or those recovering from illness.
The Role of Vitamin E in Horses
Vitamin E, primarily in its most active form, alpha-tocopherol, serves as a potent antioxidant. Its primary role is to protect cells from oxidative damage, which is particularly important in the muscles, nervous system and immune cells. Oxidative stress arises when free radicals, unstable molecules generated through metabolism or environmental factors, accumulate and cause cellular damage. Vitamin E neutralizes these free radicals, preventing the destruction of cell membranes and other essential cell structures.
Horses, being athletic animals with high metabolic rates, are particularly susceptible to oxidative stress, especially during periods of intense exercise, illness or injury. Therefore, vitamin E is crucial not only for protecting muscle and nerve tissues but also supporting immune function, which in turn helps with disease resistance and recovery.
Equine Immune System
The immune system is a horse’s primary defense against infections, diseases and other foreign invaders. It comprises two key components: the innate immune system (the body’s first line of defense) and the adaptive immune system (which involves more specific responses, including the production of antibodies).
Vitamin E plays a significant role in modulating both innate and adaptive immune responses. Here’s how it affects different components of the equine immune system:
- Antioxidant Defense for Immune Cells: Immune cells are highly active and produce a large amount of free radicals during an immune response. Without adequate antioxidant protection, these cells can suffer from oxidative damage, reducing their ability to fight infections effectively. By neutralizing free radicals, vitamin E helps preserve the integrity of immune cells, enabling them to function optimally during an immune response.
- Enhancement of Phagocytic Activity: Phagocytosis is a process where specialized immune cells, such as macrophages and neutrophils, engulf and destroy pathogens. Vitamin E enhances the efficiency of these cells, ensuring that invading bacteria, viruses and other harmful agents are rapidly neutralized. This boost to the innate immune system means that horses with adequate levels of vitamin E are more likely to fend off infections at an early stage.
- Improvement in Antibody Production: Vitamin E is also involved in the adaptive immune response by influencing the production of antibodies, which are proteins that specifically target and neutralize pathogens. Studies have shown that vitamin E supplementation can lead to an increase in antibody titers (concentration) following vaccination or exposure to pathogens, which means that horses are better prepared to fight infections and are more responsive to vaccinations.
- Reduction of Inflammation: Inflammation is a natural immune response to infection or injury, but chronic inflammation can lead to tissue damage and a weakened immune system. Vitamin E has anti-inflammatory properties, helping to regulate the inflammatory response and prevent excessive tissue damage. In horses, this can be particularly beneficial in reducing inflammation-related conditions such as arthritis or respiratory diseases.
- Support During Stress and Illness: Horses undergoing stress, whether from training, transportation or illness, are at higher risk of immune suppression. Stress can increase the production of cortisol, a hormone that can suppress immune function. Adequate levels of vitamin E help mitigate the effects of stress on the immune system, ensuring that horses maintain their disease-fighting capabilities even during periods of physical or emotional strain.
Vitamin E Deficiency in Horses
Given the crucial role of vitamin E in the immune system and other physiological processes, a deficiency can lead to a variety of health issues in horses. Deficiency often occurs when horses have limited access to fresh pasture, as dried forages like hay and processed feeds contain significantly lower levels of vitamin E.
Some of the primary symptoms and conditions associated with vitamin E deficiency include:
- Weakened Immune System: Horses deficient in vitamin E are more susceptible to infections and may exhibit slower recovery times from illness or injury due to compromised immune function.
- Equine Motor Neuron Disease (EMND): This degenerative disease affects the muscles and nerves in horses and is strongly associated with vitamin E deficiency. EMND is a progressive condition that can lead to muscle wasting, weakness and eventually death if left untreated.
- Muscle Disorders: Without adequate vitamin E, horses can develop conditions like exertional rhabdomyolysis (tying-up), where muscles break down after exercise, causing pain and stiffness.
- Poor Coat and Skin Health: In some cases, a deficiency in vitamin E can manifest as poor coat quality or skin problems, as the vitamin is essential for maintaining healthy cell membranes.
Sources of Vitamin E for Horses
To ensure horses receive enough vitamin E, owners and caretakers must pay close attention to their diets. Fresh pasture is the best natural source of vitamin E, as green grass is rich in this nutrient. However, horses that are on restricted grazing or those that primarily consume hay may require supplementation.
There are two main forms of vitamin E supplements available for horses:
- Natural Vitamin E (d-alpha-tocopherol): This is the most bioavailable form of vitamin E, meaning it is absorbed and utilized more efficiently by the horse’s body. Natural vitamin E supplements are often recommended for horses with higher needs, such as those in intense training or those recovering from illness.
- Synthetic Vitamin E (dl-alpha-tocopherol): While synthetic vitamin E is more commonly found in feeds and supplements, it is less bioavailable than the natural form. However, it can still provide adequate vitamin E when administered in higher doses.
Supplementing Vitamin E for Optimal Immune Function
For horses that do not have access to fresh pasture year-round or those under heavy physical demand, vitamin E supplementation can be a critical part of maintaining a healthy immune system.
Supplementation is particularly important for:
- Performance Horses: Intense exercise generates more free radicals, increasing the need for antioxidants like vitamin E to prevent muscle damage and support immune function.
- Older Horses: Aging horses may experience a decline in immune function, and vitamin E can help support their immune response, reducing the risk of infections and illness.
- Horses with Chronic Conditions: Horses with conditions such as equine asthma or those recovering from surgery or illness may benefit from increased vitamin E to support healing and reduce inflammation.
About Tania Cubitt, PhD
A native of Queensland, Australia, Tania Cubitt, PhD, received a bachelor of science in animal science at the University of Queensland before receiving her master of science degree in equine nutrition and growth at Virginia Tech University. She went on to receive her doctor of philosophy degree in equine nutrition and reproduction also at Virginia Tech. Cubitt currently works as an equine nutrition consultant at Performance Horse Nutrition and focuses on developing feeding strategies for horses with special needs.
