Just curious about this. A friend's friend acquired an ex-racehorse about a year ago. He had been living in Kentucky in an open pasture with a loafing shed. He had one other (three y.o.) horse for company. He was VERY quiet for a tbred, especially one off the track; had good conformation and was shaping up to be a good riding horse. Mother's Day weekend was cold and rainy. They went out to feed the horse Sunday night, and found him lying dead in the field. What would cause a sudden death like this? He had no prior visible symptoms, according to them, and no marks on the body. Someone else said horses don't have heart failure, unless it's an aneurysm while excercising, or strokes. Is this true? He was less than ten years old.