We have a herd of Dexter cattle and they are fed only on our grass and sileage and hay - no cereals at all for them (doesn't help you much with your birds does it!) They are a traditional breed and produce delicious beef - and the advantage of purely grass fed is that the meat has two to six times more Omega 3 fatty acid than cereal raised beef.
How much land have you got? Enough for a couple of cows?? Dexters are only small