Quite true about the minerals not helping much. However, if you go on over to the hill country or farther west, the antlers get larger. I think it's the calcium, which is in much larger quantities than the trace minerals in a salt block. Places where you can grow alfalfa should have deer with larger antlers. (You can't grow alfalfa in east Texas, 'cause there isn't enough lime/calcium in the soil).
I never saw a rock in Brazoria county that wasn't imported, so we obviously didn't have limestone to help the crops. Alvin, home of Nolan Ryan and the record rainfall for the US, is known as the area for ROC (rice, oil and cattle), but not alfalfa. Bay City is probably similar.