Until recently I was the H&S officer for the local wildfowling club and had to write risk assesments including cattle in fields.
Cattle are big and protective of their young.
It's simular to riding a motorbike on the road, treat everything and every person as if it wants to kill you and you will survive.
1 Don't go into a field with cows and calves if you have a dog.
2 If you do keep an eye on the cattle and if they approach take the lead of the dog, it can run faster than you and the cows.
3 Stay close to the bounderies.
4 Do not run, a cow will always out run you.
5 Now we get to the brave bit, I worked with cows for 10 years, most are only inquisitive and will bound at you, don't run away, they will run you down, run at them they will scatter. I can guarantee it.
6 It doesn't work if they have small calves, they will just have a great time enjoying themselves jumping up and down on you.
7 Never take your eyes off the cattle.
8 Now the most difficult bit, use common sense.
Have a good day.