http://www.minecraftforum.net/viewtopic.php?f=1&t=15784"Minecraft Ranching
Wouldn't it be cool to raise pigs and sheep Keep them alive in an enclosed space without them disappearing?
Some ideas that have been brainstormed:
Fences - to keep your animals together and not escaping
Feeding - when you feed a pig, you'll get more meat when you kill it. When you feed a sheep you'll get moor wool when you shear it.
Hunting mobs - At night many mobs will try and kill your livestock. This would provide you with more to do than hide during nights and instead you have to protect your animals."