Selenium is a so-called trace mineral, a mineral of which very small amounts are needed for good health. Selenium performs several important functions in the body:

• Selenium is an antioxidant and, along with vitamin E, plays an important role in muscle metabolism
• Selenium is also important for the production of certain (growth) hormones
• Selenium plays an important role in resistance, brain and nervous system functioning

Selenium deficiency can result in decreased resistance and fertility, reduced growth, stiffness or lethargy. Excess selenium, on the other hand, is toxic and can cause sweating, tremors, colic, diarrhea, increased heart rate and breathing.

In roughages, selenium occurs primarily in the form of selenomethionine. This is an organic form of selenium in which selenium is bound to the amino acid methionine. However, many soils are too poor in selenium so most roughages and grains also contain too little selenium to meet the horse’s needs. Supplementing the ration with selenium is therefore necessary.

There are several selenium sources available that can be used in concentrate feeds and supplements to meet the horse’s selenium requirements. A recent study compared sodium selenite (inorganic selenium) with selenomethionine (organic selenium). In this study, broodmares were supplemented with either selenomethionine or sodium selenite at the end of gestation and during lactation. The main conclusions of this study were:

• Selenium supplementation led to higher blood selenium concentrations and improved antioxidant status of mares
• Selenium levels in milk and colostrum was higher in mares receiving selenomethionine (instead of sodium selenite). This also led to better selenium and antioxidant status of foals from mares receiving selenomethionine
• Evidence that selenium (and particularly selenomethionine) has a positive effect on bone development in growing foals

This research once again shows the importance of selenium and the difference in effectiveness of different sources. VitaMinalia naturally uses the most effective selenium source, selenomethionine!

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