I had tons of questions about joint supplements, too, when I decided to start Mudpie on one. The folks at SmartPak helped me IMMENSELY. I strongly recommend that you call and chat with one of the representatives. They're extremely knowledgable and patient, and will answer all of your stupid questions. I recently talked to one for a straight hour, with all sorts of weird questions. :)
I've been repeatedly impressed with their customer service.
Check them out, and call them up to ask about what would be best for your horse!!
Their website is HERE