Welcome from Portsmouth. A local farmer I know has a Rottweiler and his dog is a friendly old soul but when I'm hiking (or running) I find that dogs can often be a bit unpredictable, both big and small ones. For me, farmyards are the places to worry about, what's lurking behinds sheds etc? And then, of course, there are cows, geese and ducks to take note of. I've never yet had a problem with sheep or horses, although in 2019 a horse did creep up behind me, took my hat off of my head and then dropped in on the grass a few yards away!