Ive never had much issue with cows, its the bullocks i find very intimidating and very unpredictable.
Cows are usually quite docile, and if you do not alarm them, or scare them by making unnecessary noise, then they usually leave you alone.
Many years ago, whilst living in South Wales, i almost came to grief with a large herd of bullocks, who started to gallop at some speed towards me, when i was already in their field, and when i had reached the safety of the bridleway gate, they were still in a very frisky state.
As for farm dogs or guard dogs in general, some years ago near Hirwaun in the South wales valley's, i visited the large car scrap merchants looking for a spare part for my Escort.
The two alsatians in the Ford Transit, were mental with rage, the van was physically moving when they sensed my presence, give me a field full of frisky cows any day, very scary.
Its horses i distrust the most, and if your in a field with a stallion, then you have to be constantly vigilant.
Daft as it might seem, i usually make a detour around a field full of cows or horses, and if that detour is a lengthy one, so be it.
Cows can easily outrun a fit walker, so better to be safe than sorry.