When we were kids we used to go into one of the local fields and when the cows approached stand still and they would come up and sniff at you and leave. These were milking cows close to the farm so I don't know what they would be like on open moor or whatever. My approach on Dartmoor is to walk very quickly towards them and they usually move off,but I always looking back after passing as I have been followed and had to run more than once.
Peace Lubin