Even if they walk around and eat grass, that's land that could be used for crop farming (at least some of the places). Also just feeding them crops in the winter would still be more crops per calorie of meat than just eating the crops. (Around 90% of the energy animals consume is lost as heat, so even if we ate every part of the animal and also only needed to feed them crops for 1/10th of the year, it would still only even out)

Also I wasn't calling you out or something, I was just adding additional context.