I think it is good for lambs to have the feel of a halter at a very young age. I normally am showing lambs born in April, at a show at the end of May, and find that by the end of the show (if not at the start!) they are leading pretty well. Mine are Castlemilk Moorits. Even if you are not showing it is really useful to have halter trained sheep, especially if you have a small flock, and they learn fairly quickly. The trick is to give little tugs rather than fight all the time, and reward with a treat (if they will take it from you) or just release the pressure every time they step forward. Good luck...