Always worth having a few quid handy in case a bull decides to charge you.
Bullocks though I reckon just gallop up for a laugh. I've walked walks (I do lots) where others arriving at tearoom tell me of their narrow escape yet I've had no bother through the same pack. Turn and face them and they'll stop. They are curious and will usually sidle right up and even give you a lick but raise a hand and they're off.
I always greet them.
Cows with calves are best circumvented.