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Most NZ horse owners are aware that parts of this country are deficient in selenium, one of the most important trace minerals, but the tragic deaths of 21 top polo ponies in Florida emphasise the fatal effects of selenium overdose.  Selenium, while necessary to health, is also very toxic in the wrong quantity.

As a matter of routine the Venezuelan Lechuza Caracas polo team horses are dosed with Biodyl, a commercial dietary supplement made in the USA but not FDA approved in that country, although widely and safely used elsewhere over more than 50 years.   Its main ingredients are Vitamin B, potassium, magnesium and selenium and it is intended to reduce travel stress, prevent azoturia (exertional rhabdomyolysis) and enable quicker recovery from hard exercise. 

The team management instructed a Florida compound pharmacy, which then wrongly mixed a vitamin and mineral supplement, apparently intended to replicate the effects of the commercial supplement.  The 21 ponies that were dosed with it on the day of an important match died; five remaining team ponies, which did not receive the supplement, were fine.   The pharmacy confirmed that the error was with an excess quantity of selenium selenite.

While selenium is essential for the health of the horse, it has to be administered with great care and it is far safer to use chelated selenium, like VetPro’s Selenium-K because it would be almost impossible to overdose the horse if delivery instructions are followed.   Chelated minerals are more easily absorbed, being bound to amino acids (proteins) to enhance availability (think calcium in milk and iron in red meat), which body cells perceive as food. The protein is digested and more of the mineral in question will be utilised in the cells.  Essentially, in chelation, sometimes called organically complexed, the inorganic compound is altered to an organic state.

Vets often prescribe liquid selenium, which is not chelated, and the very small quantity required for safe dosage must be accurately measured or overdosing can occur, leading to toxicity.  It’s worth having the soil on which your horse grazes tested, which will give an accurate guide to what is and what is not required in supplementation.   However, if there is a selenium deficiency, play safe and look for a chelated product, of which VetPro Selenium K is one of only two products specifically designed for horses. 

(For further info, read the article on Selenium Toxicity in our “Equine Vet Talk” pages)

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