As Lodious said, I would be more worried with a cow and a new born calf in the field.
Saying that, a friendly bull can be more dangerous than a nasty one.
As mentioned, its easier to take your eye of a friendly one and next thing you know you are a scratching post next to a fence 😉
I have seen a bull push over a six foot brick wall as if its not there, jump a picup.
Years back, feeding stock hay one winter out of a picup, had a bull with an itch get its head under the rear axel of the picup and lift it as if it was a cardboard box with me in the back!
Prompting me to do one over the picup roof and the quickest 80m dash you have ever seen 😉
Everyone knows the only dangerous animal on a farm it the farm owner, very short tempered and unpredictable 😉
Back to the OP, the only other time I would avoid a heard of cows in a field is when they are first let out after being stuck in all over winter, pretty obvious though if you see it happen 😉