Can I just say what a brilliant and timely thread this is! For the last month I have been "chased" by bullocks on nearly every walk I've been on (the visit to Boy's Grove round barrow was actually the result of me hopping over a fence to avoid a closer encounter than I would like). I always carry a rucksack, have no dog and probably spend most of the time looking shit-scared!! I never used to mind them at all, but now I've started planning routes to avoid fields with cows in (which is difficult as the OS map doesn't show cows, annoyingly. Need one of those maps off Harry Potter).
Anyway, I'll try facing down a few sheep and then work on my calmly-ignoring-cows zen thing. I don't eat meat, perhaps they can smell carnivores and realise I'm no threat to them!
Last time we went to Boscawen-Un I got bitten on the bum by a goose, while my girlfriend laughed (and made her escape). :-)