Selenium (Se) is an antioxidant mineral that is necessary in the horse’s diet. Horses derive selenium by consuming hay or grasses that grow in soils that contain this trace mineral. However, if you live in a region with low selenium levels in the soil, your horse’s forage may be deficient in this essential mineral.

Not getting enough selenium in the diet can contribute to a wide range of health problems for your equine companion. It can impair muscle function, heart health, immune function, growth and energy levels in your horse.

So how common is low selenium in horses? If you live in the coastal regions of North America, near the Great Lakes, or in most parts of Canada, your soil levels are known to be low in this mineral. Selenium supplements or enriched feeds are necessary to support the health and well-being of your horse.

Selenium toxicity is also a concern for horses that get too much of this mineral. However, deficiency is a much more common problem and selenotoxicity can largely be avoided by supplementing with organic sources of this compound, rather than inorganic sources found in many feeds and supplements.

Mad Barn’s Omneity Equine Mineral and Vitamin Pellet contains 2.4 mg of organic selenium in a typical serving size. In addition to selenium, Omneity also provides all other essential minerals and vitamins that your horse needs in a science-backed formula designed to balance all different types of forages and diets.

Why Horses Need Selenium

Selenium is a micromineral that horses need to ensure optimal antioxidant defenses in the body. It is particularly important for horses during periods of growth or increased performance demands.

According to one source, 30% of horses are low in selenium. [5] Another source suggests that greater than 50% of horses in the United States do not get enough selenium from their forage alone. [6]

Racehorses, horses in heavy work and young foals are at the highest risk of insufficient levels of this mineral. [1]

Below are the top 7 reasons why horses need adequate selenium in their diet:

  1. Selenium is a key component of the antioxidant enzyme glutathione peroxidase. This enzyme helps to neutralize free radicals in the body and is involved in liver detoxification pathways. [6]
  2. It is necessary for the function of the acquired immune system, helping to protect against infection and disease.
  3. It plays a critical role in thyroid function and the type I iodothyronine 5-deiodinase enzyme which regulates the availability of T3 – the active form of thyroid hormone. Thyroid hormones control metabolism in the body. [9]
  4. Selenium is required for equine muscle development and growth. Along with Vitamin E, it is a component of proteins that prevent muscle conditions such as tying up (nutritional myopathy or exertional rhabdomyolysis). [8]
  5. This essential mineral is also important for reproductive health. Inadequate levels can lead to infertility and reproductive complications.
  6. It is known to prevent white muscle disease in which white scar tissue develops in the skeletal and cardiac (heart) muscles of horses. This can lead to rapid heart rates, difficulty swallowing, recumbency, weakness and urine discoloration. [1]
  7. Selenium is a component of the amino acid selenocysteine – an essential amino acid. It is required to synthesize 30-35 different selenoproteins with a range of cellular functions that continue to be researched in horses.

Signs of Selenium Deficiency

If your horse does not get enough of this nutrient in their diet, they may display some of the following signs. Horses that have a greater degree of deficiency and those engaged in more intense training display more serious symptoms. [8]

  • Cribbing
  • Stiff gait
  • Muscle soreness
  • Lethargy
  • Diminished performance
  • Muscle spasms, trembling or twitching
  • Problems with chewing and swallowing
  • Atrophy of muscle tissue
  • Heart failure
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