One hundred horses are dead in Marion County after coming down with a strange illness.

The horses at the Equitransfer Farm were euthanized after they began showing signs of what appeared to be a neurological disorder. Equitransfer is a company that takes eggs fertilized from mares and plants them into surrogate horses. Owners Jose Davilla and Francis Ramirez said they noticed some of their horses showing strange, seizure-like symptoms about one week ago. Davilla said the culprit could be the hay the horses were fed because that type of hay is prone to growing bacteria. The hay, and some of the horses, were sent across the country to be tested.

The type of hay, haylage, is usually fed to cattle. But Equitransfer has theirs specially made.

“It's fed with a special inoculate inside it so that we can feed it to horses,” Davilla said. “It has a higher protein source than regular hay.”

Although the cause won't be determined until the test results are back, the owners said they believe moisture in the haylage could have fostered an environment for bacteria to grow.