OP, how are your horse's joints? At 22 he might benefit from a joint supplement like OneFastHorse said. There's a dizzying array of products available, and unfortunately what works well for one horse doesn't necessarily work as well for another. You may need to try a few brands to see what works better for your horse. In general, cheaper products are using ingredients that aren't as high-quality and are not as bio-available. This is one case where you really do get what you pay for. According to two different vets I've asked about joint supplements, you should make sure that the one you're giving to your horse contains glucosamine, chondroitin, MSM, and hyaluronic acid (HA). Some people will say that a supplement needs to contain at least 10,000mg of glucosamine to be effective, but you can do your own research on that particular subject.