Dr. Martin Adams, Equine Nutritionist for Southern States

Selenium is a trace mineral that is essential to good health in the horse.  Selenium is incorporated into proteins to make selenoproteins, which are important antioxidant exzymes that have several functions in the horse’s metabolism.  Selenium-requiring enzymes provide antioxidant protection to prevent cellular damage from oxidation, which occurs in every cell of the horse’s body.  These selenium-containing enzymes also have roles that control growth, immune function and reproduction.
Forages (hay and pasture) are the major dietary source of selenium for horses, and selenium intake depends upon the amount and availability of selenium in the soil in which the forage is grown.   The eastern and western United States have below normal levels and/or availability of soil selenium.  This results in forage that can provide an inadequate amount of selenium for the horse’s dietary requirements.  Supplementation through concentrate feeds and mineral supplements can be necessary to prevent selenium deficiency and to maintain normal growth, reproduction and performance in the horse.

The National Research Council recommends 0.1 parts per million (ppm) of selenium in the total diet for all ages and classes of horses.  A level of 0.1 ppm selenium is probably sufficient for mature idle horses, but requirements for growing horses, broodmares and performance horses need to be higher, on the order of 3 milligrams (mg) per day or 0.3 ppm selenium in the total diet.  For example, a daily feeding program that provides ten pounds of Legends Horse Feed (containing 0.6 ppm selenium) and fifteen pounds of hay (containing 0.1 ppm selenium) will result in a selenium intake of 3.4 mg and a dietary selenium concentration of 0.3 ppm.

Because of the research-proven benefits of organic selenium and the recent clearance by the Food and Drug Administration for the inclusion of organic selenium in horse feeds, all Legends and Triple Crown horse feeds now contain organic selenium as the sole source of selenium.  This product is a natural form of selenium which is produced through a yeast culturing process and is called selenomethionine.  This type of selenium is absorbed better and is less toxic than sodium selenite, the inorganic selenium source previously used in horse feeds.  This new additive is listed as “selenium yeast” in the list of ingredients.

Benefits of organic selenium include:

• Greater retention of organic selenium in exercising horses, allowing better antioxidant protection for performance horses.
• Higher blood selenium levels in pregnant broodmares, resulting in better immune response for increased placental expulsion and increased fertility in foaled mares.
• Higher levels of selenium and immunoglobulins in foals nursing mares receiving organic selenium, resulting in better immune response and healthier foals.