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Equine Nutrition: Selenium

This is the second post in my nutrition series. If you missed the first one on vitamin E, here it is.

As equestrians, we want the best for our horses and part of that is understanding nutrition. As a horse and barn owner, I’ve always had an interest in digging deeper into recommendations from equine experts.

This week, I read through these two articles and summarized their notes and recommendations below for you:

Keynotes on Selenium in Equines

  • Selenium, an essential nutrient that horses get from grazing, is an antioxidant. It is also used in Thyroid function, muscle function, and immune system. It can also help prevent certain forms of cancer.
  • The soil in North America is poor in selenium, so pastures are equally poor.
  • Horses who work hard, such as endurance mounts, may require additional selenium.
  • Selenium and vitamin E go hand-in-hand: deficiencies in Vitamin E or Selenium can be compensated for if the other is plentiful.
  • Supplemented selenium has a good absorption rate compared to others.
  • A total of 3 mg of selenium daily is enough for most horses
  • Selenium deficiency can be hard to identify if the horse receives enough vitamin E, early signs include work intolerance, poor hair coat, and early onset of problems related to ageing.

What to do

Evaluate current feed—Look at the selenium content in your hay and other feeds and grains, if they are at 3 mg, awesome!

If Selenium deficiency is suspected—contact your veterinarian to have a blood test done. With advice from your veterinarian, add a selenium supplement to your horse’s diet. Careful—Work with your veterinarian to calculate how much selenium is currently in the horse’s diet, forage and grains), then supplement. Too much selenium and selenium toxicity can happen fast and be deadly.


Selenium is an essential nutrient for horses in North America, so it should be supplemented and in cases of deficiency, consult your veterinarian.

Hungry for more? Here is the next post in the series Equine nutrition: Biotin.

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