Goats eat just about anything, so very good with a weedy spot. One of ours tried to eat my wool jumper whilst I was wearing it So they do need to be properly fenced in, they can get over lower fences and push their way through. Sheep are easier to keep contained and fussier with food, they love grass and will eat it right down till they end up eating dirt and then make themselves sick (well this is what we were told by others who have them)