Think about it, if you don't put your livestock in a fenced area, there going to go wander off. I say I just gave them a better home.
Watch out--even if you put your livestock in pens or rooms, they can glitch out. Sheep are notorious for doing this if you have a lot of them in the same area together. A good solution is to make your walls 2 blocks wide, and to give your livestock lots of horizontal space.
