Cows never bothered me in the past - big intimidating animals, but the usually don't do much when you pass them by.
I sometimes walk along the river where the farmer sometimes lets his cows enter to graze. It's a popular public area and footpath region that curves around the outskirts of town, so I question why he does this. Anyway, they were blocking my path so I decided to walk around them. Wasn't much room so I had to get quite close to the heard. I got "butted" several times, quite hard, but luckily none managed to knock me over - quite frightening! I didn’t have a dog or anything.
I looked back and saw they had some younger carves in the group. So yeah, be careful. Most the time nothing happens (this was the first time and I’m out walking/riding all the time), but they can get defensive (herd animals do fight back at dangers to the group), especially if they have carves - don't take their placid nature for granted!
Just use a bit of common sense - give them a little space when passing.