Continuation of an article by ©2005 By Deb Bennett, Ph.D.:
What Does it Mean to “Start” a Young Horse?
Let us now turn to the second discussion, which is what I mean by “starting” and the whole history of that. Many people today – at least in our privileged country – do not realize how hard you can actually work a mature horse – which is very, very hard. But before you can do that without significantly damaging the animal, you have to wait for him to mature, which means – waiting until he is four to six years old before asking him to carry you on his back.
What bad will happen if you put him to work as a riding horse before that? Two important things – and probably not what you’re thinking of. What is very unlikely to happen is that you’ll damage the growth plates in his legs. At the worst, there may be some crushing of the cartilages, but the number of cases of deformed limbs due to early use is tiny. The cutting-horse futurity people, who are big into riding horses as young as a year and a half, will tell you this and they are quite correct. Want to damage legs? There’s a much better way – just overfeed your livestock (you ought to be able to see a young horse’s ribs – not skeletal, but see ‘em – until he’s two).
Structural damage to the horse’s back from early riding is somewhat easier to produce than structural damage to his legs. There are some bloodlines (in Standardbreds, Arabians, and American Saddlebreds) that are known to inherit weak deep intervertebral ligament sheathing; these animals are especially prone to the early, sudden onset of “saddle back’” However, individuals belonging to these bloodlines are by no means the only ones who may have their back “slip” and that’s because, as mentioned above, the stress of weight bearing on the back passes parallel to its growth plates as well as parallel to the intervertebral joints. However, despite the fact that I have provided a photo of one such case for this posting, I want to add that the frequency of slipped backs in horses under 6 years old is also very low.