Vitamin E and selenium are two essential nutrients commonly found in high-quality pastureland or hay. These nutrients play a role in many essential functions and should be a mainstay in a horse’s diet. However, what exactly are they and why are they important?
Vitamin E is a collective term for eight compounds known as tocopherols and tocotrienols. These compounds are fat-soluble vitamins that play a critical part in a horse’s neuromuscular health. The National Research Council, or the NRC, recommends horses to consume 1000-2000 IU (international units) of vitamin E per day for an average, 1,100 lb. horse. If a horse does not receive this recommended amount, it is at risk of becoming vitamin E deficient. There are several dysfunctions a horse could develop from this deficiency, including equine motor neuron disease (EMND), vitamin E deficient myopathy (VEM), and equine neuroaxonal dystrophy/equine degenerative myeloencephalopathy (eNAD/EDM). Developing dysfunctions such as these depends on a horse’s extent of deficiency, genetic predisposition, and when in the horse’s life the deficiency occurs. In a short-term deficiency, a horse shows recognizable signs such as muscle soreness and poor performance. For a longer-term deficiency, a horse could fully develop VEM.
All forms of vitamin E can be found in high-quality pastureland or hay. If a horse is kept outside on good quality grassland, it will likely meet the recommended amount of vitamin E, oftentimes surpassing the suggested intake amount, depending on the soil’s moisture. Hay contains traces of vitamin E, but at much smaller quantities. The amount in hay is not stable when exposed to heat and drying. It is recommended that a horse on less than twelve hours a day of pasture receives supplemental vitamin E, especially if the pasture is poor or the horse cannot maintain a healthy weight. Always consult with an equine feed nutritionist or a veterinarian before changing a horse’s diet to determine whether your horse requires supplemental vitamin E. It is especially important to have your horse checked by a veterinarian if it already has a neurological condition that is worsened by lowered vitamin E levels.
Selenium, the mineral commonly referenced with vitamin E, is a trace mineral and antioxidant that is incorporated into proteins to form selenoproteins. This mineral is just as vital as vitamin E in a horse’s neuromuscular health, as imbalances can upset this function. It is also an essential part of the enzyme glutathione peroxidase; this enzyme protects cells from oxidative damage during the metabolic process. Selenium also prevents the development of white muscle disease in horses.
Selenium is found in forages (grass and hay) and grains. The amount of selenium in forage depends on the pH level and the selenium content in the soil. Pastures in Central Kentucky are known to have a low to marginal selenium content. Found in either an organic or inorganic form, commercial feeds usually have one of either form of selenium incorporated into the feed and labeled on the bag. The National Research Council recommends a minimum of 1 mg selenium per day for mature, 1,100-lb. horses and 1.25 mg per day for lactating mares or heavily exercised horses. Some high-performance feeds contain up to 0.6 mg/kg of selenium to maximize antioxidant benefits.
Vitamin E and selenium are linked nutrients – a deficiency of one can be compensated if there is an adequate supply of the other. If both nutrients are inadequate, then there is a potential for a horse to develop oxidation-induced damage to muscle tissue. Therefore, it is important to ensure a horse receives adequate amounts of both.
All Excel Equine®® feeds are fortified with vitamin E and selenium to meet the needs of each horse. For example, Performance 12®, a feed from our performance blend line, contains higher levels of both vitamin E and selenium to meet the elevated nutrient requirements of horses in hard work, such as top-level sport horses or racing Thoroughbreds. This feed has 0.6 mg/kg of selenium and 150 IU/lb. of vitamin E. Adequate supplies of both nutrients ensures that high performance horses have strong cells and muscles.