Ask The Equine Nutritionist

I have been hearing about selenium deficiency, and I was thinking of giving my horse a selenium supplement. However, I also know that it is toxic if its fed too much. So, I was wondering, what is considered a toxic level for horses? How much selenium should a horse be getting, per day? My horse weighs about 1100 lbs.

I know I need to have my feed and pasture analyzed, but I want to make sure I don't over supplement the selenium, if it turns out that my feed/hay/pasture is deficient.

Certain parts of the country are selenium deficient. If you live in a selenium deficient area it might be worth supplementing.
Bear in mind the feed companies already supplement the feed with selenium in deficient areas.

One way to assess the horses selenium status is by measuring the serum selenium level or by measuring the selenium dependant glutathione peroxidase status. Serum selenium levels of 0.09-0.30mg/L indicate adequate selenium intake.

In selenium deficient areas an intake of 10-15g of selenium salt will provide adequate SE. Toxicity will occur at an intake of 454g per day or
more. An overall intake of 5mg/kg (ppm) is considered toxic. When you supplement with selenium you also usually supplement with Vitamin E as Vit E and selenium are closely involved with each other.

Dr. Melyni Worth Ph.D. - 2004 (c)

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