In the UK pretty much all farmland (whether arable or pasture) is permanently enclosed, usually by walls or hedgerows. In many countries, including the US and some European countries there is often no barrier around arable fields, just a track or a strip of grass.I don't understand your point. Apologies for being 'thick', but electric (or plain wire) fences are a physical boundary.
In many parts of Switzerland the only barrier around pasture is a temporary electric fence which is a fairly modern invention and is not left in place around empty fields. Alpine farmers (pre electric fences) would have used other methods to corral their cattle instead of a physical barrier. In many cases goats and cows would roam the mountains relatively freely, with a reliance upon bells to aid in finding them.