Question
How do I know if my horse's diet is low in selenium? Per various maps I've found on Internet, I live in a selenium-deficient area. What should I do if I find my horse's diet is low in selenium? His stats: six-year-old Quarter Horse gelding, 16.1 hands (165 cm), maybe 1,200 lb (545 kg). His diet: Pretty good pasture for 10 hours a day (when it's growing season), piles of grassy hay (made from the back acreage on the farm) whenever he's inside, and a pound of a locally manufactured sweet feed in the morning and night. His exercise: aside from the pasture wandering, he and I fling ourselves over little jumps a few times a week, but neither of us likes to break a sweat. Help, please.
Answer
Though horses require very little selenium, the mineral is unquestionably an important player in normal physiology. One of selenium’s most well-known uses in the body involves its antioxidant properties. As you pointed out in your query, regional differences in selenium soil concentrations have been mapped by scientists, and this may prove important to your horse.
The minimum requirement of selenium for horses, according to the National Research Council in its Nutrient Requirements of Horses, is 0.1mg/kg of diet. Receiving 1 mg of selenium daily would meet the minimum requirement for a 1,000-lb (450-kg) horse. Optimal selenium consumption for the average or exercised horse would be higher, within the range of 2.5 to 3 mg per day.
The best way to determine if your gelding is receiving optimal nutrition is to enlist the services of an equine nutritionist. The details you provided in your inquiry are enough for me to make general observations, but some more detailed information, including hay and pasture analysis, would be most useful.
Most commercial horse feeds contain sufficient selenium to meet requirements if they are fed according to the manufacturer’s instructions. At 2 lb (1 kg) per day, I would guess your gelding is not receiving what the manufacturer intends. If feeding the recommended amount supplies too many calories, you can always add a ration balancer, which provides a concentrated source of protein, vitamins, and minerals, including selenium.
Because of the elevated antioxidant requirements for athletic horses, Kentucky Equine Research (KER) developed a product that provides complete antioxidant support, including organic selenium, natural-source vitamin E, vitamin C, and magnesium. Preserve PS contains 2 mg of selenium (per 30 g) to meet requirements for horses in need of additional supplementation. Do not feed more than one supplement containing selenium as an overload can cause toxicity. In Australia, look for Preserve for optimal selenium support.
