Okay I've read that horses fuse from the bottom up and the vertebrae are the last to fuse (around 6-7 years old). I vaguely remember hearing/reading something about a young horse being able to slip a disk if asked to collect too early? Is this true and if so how long would you wait to introduce collection? Would working on extensions cause any damage (if done lightly) to a 3/4 year old?
For you horse health gurus I'd love to know anything and everything about working the young horse and how slow to take it/how it effects the horse. I don't plan on riding my horse till he's three. I'll be waiting till four for canter work so three year old year will just be getting used to leg, seat, and reins aids as well as some more on the trail despookifying (we're already working on that).