In planning for my own homestead (that I'll never have) I too thought about fencing. Fencing is expensive and take a lot of work to put in and maintain. And then the cows go and rub themselves on it and push it over. (and they will lick the paintwork off your car too!)
So how about having an organic fence? String up blackberry etc on a lattice using the trees that are already there for supports. you get really nice barrier, especially if to make it several feet wide, that no-one will want to cross, and you also get berries for your icecream. :-)
It might take a couple of years for it to be fully established, but once it is there it will just keep on getting higher and thicker, and more full of berries.
Just a thought.
Great idea @trevor.george, don't use gorse though....it's horrible OR barberry...they are the curse of the NZ countryside. Berries are all good :)
or boxthorn!!! Those things will go right through the sole of your boot!
I spent a bunch of time on my aunt's farm when I was a kid ripping out boxthorn hedges.
Nasty stuff!