Risk Of Riding To Early
It's important not to start riding a young horse too early in his development, as it can cause both physical and physiologically damage. Different breeds grow at different rates. Most horses reach their full adult height between the ages of 4 and 5, but some heavy breed won't reach their full height until they are around 8 years old.
Skeletal maturity is very important factor when starting a horse. Horses have growth plates on either end of every bone in their bodies, other than their skull, which allows bones to grow. These plates at the end of their bones are made from cartilage, but once they have finished growing they convert to bone and become more durable and less susceptible to damage. The plates belonging to bones that involved in how tall a horse gets like the femurs and hocks--usually fuse by around 4 years of age. The bones of the vertebral column are the last to fuse and rarely do so before a horse is 5 1/2 years old.
You must also consider the emotional maturity of the horse as well. Those who are worked too early may have trouble understanding what you're asking of them because they are simple not mentally ready for complex commands yet. Most horses reach emotional maturity between 5 and 7 years of age. If you ask a horse to do to much before he reaches his emotional maturity it cause significant problems. The horse may become resentful of their work, which can cause unwanted behaviors.
Riding to early can be risky. While you don't have to wait for your horse stop growing completely and all his bones to be fused to get on his back, it not advisable to start riding him too soon. While rare riding to early can cause leg deformities or damage growth plates , but it can happen. Spinal problems can be an issue as well when riding a horse that is too young. To avoid these problems it is best not to ride your horse much before he is at least 4 years old and some people prefer closer to 6 years old.
Ground training lightly can begin between 2 and 3 years of age. When your horses reaches 4 years of age you can begin more rigors ground training that will be a foundation for his saddle training. When he reaches his 5th year you can begin to do some light riding and training. The more advance training and riding should wait until he is 6 years old. You want your horse to have a long, useful, healthy and happy live with you.