If your horse got out and got into the feed then he could develop laminitis, a potentially severe degenerative problem in the feet in which the laminae (the tissues and blood suppl to the hoof) that hold the hoof on dies and separates and they can even shed their entire hooves and the navicular bone can rotate and fall thorugh the bottom of the hoof. It can also cause colic but you need to have a vet see the horse immediatley and check his feet for heat and soreness. You need a vet to see the horse because if he does develop laminitis then walking him to help with the colic could cause permanent foot damage that can't be fixed. He can develop both colic and laminitis at the same time.