If he is having trouble keeping his foot healthy, maybe try shoeing him with pads to protect his feet. This will protect them and create less of a chance of him becoming sore. If you really want to keep him barefoot, try giving him hoof strengthening products. There are a wide variety of hoof hardeners and even supplements to encourage growth and optimal health. Also, try keeping the hooves as dry as possible and avoid thrush. This would weaken them and prevent growth.