I'm reading a book at the moment, "The other end of the leash", by Patricia McConnel who has a PhD in animal behaviour. While I haven't read anything about training dogs out of hearding habits there maybe something in her collection which may help. Try her site: www.dogsbestfriendtraining.com
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-- Murray I What part of 'no' don't you understand? Is it the 'N', or the 'Zero'?