As a reiner it is the norm to start them by now of their 2yo year. I have found from experience if a 2yo is started properly. Meaning that for the first few months you work at the walk and get them giving their face moving their body (shoulder, Mid, Hip) in the long run you will have a better broke horse and by the time they are ready to start trotting and loping they are in good shape and are ready for more. They have a good handle are able to balance your weight. There is less pressure to get them broke you have more time to get the job done so their is less pushing.