MU Vets Seeing More Horses
with Nutritional Issues This Year
-Expert warns selenium poisoning, vitamin E deficiency a result of last year's drought, bad hay

Mizzou Spotlight on Science (courtesy of KFRU)

While much of the Midwest has recovered from the drought that parched the area last year, horses are continuing to experience effects from the hot dry summer of 2006. Due to a bad hay crop, University of Missouri-Columbia veterinarians are reporting an increased number of horses with chronic selenosis and vitamin E deficiency, problems that can be fatal.

"Last year's drought meant that Missouri's hay crop, which is usually balanced very well for a horse's nutrition, was much poorer than usual," said Philip Johnson, professor of veterinary medicine and surgery. "Because of the poor Missouri hay crop, horse owners imported hay from other states nearby and possibly fed their horses hay that was too high in selenium. This can have very grave consequences for horses. Owners also may have fed their horses poor quality hay from Missouri or other places, which led to deficiencies in vitamin E, another very dangerous problem for horses."

Selenium is a naturally occurring element and is an essential part of horse diets. However, too much or too little can create problems for a horse. When chronic selenosis, or selenium poisoning, occurs from eating too much of the element, horses can lose the hair in the mane and tail and develop a form of laminitis, a painful condition that affects the hoof. If left untreated for too long, a horse with chronic selenosis may require euthanasia as a result of severe laminitis.

Johnson said that the amount of selenium in hay can vary by county throughout the nation, but that Missouri hay typically has just the right amount of the essential element. For a small fee, horse owners can have their hay tested to determine if it has the right amount of selenium in it.

In addition, hay that is not fresh can lack vitamin E, an antioxidant which is important for nerve health in a horse. Some horse owners unknowingly compensate for this deficiency by feeding their animals with nutritional supplements. Those horses that suffer from a vitamin E deficiency typically show symptoms that include weakness, loss of weight, trembling and changes in the retina at the back of the eyeball. A quick blood test can determine if the animal is suffering from a vitamin E deficiency. Johnson recommends that horse owners who imported hay from unknown sources last year either have the hay tested or keep a close watch on their horses. Horses that do not have access to green grass and that are being fed old yellow hay are at risk.

"Usually, by the time the horse is showing symptoms of either problem, it may be too late to reverse the disease completely," Johnson said. "However, if a horse owner has other horses that are feeding from the same food source, it's important to have those animals treated before the damage is permanent."

Craig Roberts, a professor of agronomy in the College of Agriculture, Food and Natural Resources at MU, says the quantity of this year's hay crop will be down 50 percent to 75 percent from normal, but the nutritional value will be good.

"Last year, we had the drought, which affected both the quantity and the quality of the hay," Roberts said. "This year, we had a late freeze, which mainly affects the yield. Overall, we will be down, but the drought last year was far worse."

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