As someone who's main hobbies are wildcamping and visiting ancient sites and mostly combining the two i've had quite a bit of experience of cattle, from the long horns by the eagle stone that look terrifying but are the most gentle beasts you could ever encounter to calves that would make your heart melt, if they weren't keeping up with you just for the sole reason to eat your gear that is, i've even camped in a field at Nether booth with a bull as the adjoining campsite was full, taking a dog into a field containing such beasts though is totally irresponsible and your just asking for trouble, not meaning to have a go here but it just shouldn't be done, ask any farmer even they wouldn't do something so irresponsible unless the dogs were fully able to cope with such a situation and the cattle had been "broke" to dogs.
Ps, one of my customers, i'm a gardener, has a herd of water buffalo, vicious looking beasts but very stable around any animal, they don't even find machinery interesting, just happy to graze as i strim and mow around their water meadow.