Cows are ruminants, they are supposed to eat grass. To feed them a different diet is somewhat cruel. Grass fed beef simply tastes better too.
I'd prefer a "hunt to eat" type of lifestyle, where the only meat consumed was that which has been hunted and harvested by the intended consumer. The majority of the human diet should be raw vegetables and fruits, with meat as the occasional supplement, not a daily gluttony of factory farmed garbage meats. The further we move away from factory farmed meats, the better we will all be for it.
Local and grass fed is really the way to go for our health and the animal's health and well being.
Go Vegan.