true , 1st you got yank them of there feet with firm no , once they realise they get hurt if they show to much interest in them, 2nd as above you got let the dog be oblivious to them, meaning there just boring things to them. But I will say this though even dogs of 5-6 years old that seen sheep from pups, have one day killed a sheep, god knows why but dogs have, even farm dogs have.!, but there just dogs not machines , and its natural for dogs to want to chase+kill sheep, never trust any dog 100% only 95%
Good post.
A line sometimes works to start with, like below..