The acreage per cow is very dependent on where you are. I have a friend with a mother who just wanted to raise cows in her retirement (and reap the sweet tax breaks of having a 'ranch'), and they support roughly 1 cow per acre with slight supplementation of food cubes during the winter. Go out to someplace that's famous for cattle like west texas, and suddenly it's a lot less,but they have so much range out there that they can let the cows go nuts.