There is no question that this is healthier for the environment, particularly in terms of reduced runoff into streams and lakes. Some researchers have found that the meat is more nutritious than that from animals raised in other systems.
Wild creatures find a more hospitable place to live in pastures.
The livestock deposit their manure all over the place, rather than having it go to some holding area that is a big environmental risk. But some graziers buy in feed or still raise corn and soybeans because they just can't attain the quality of carcass they need on straight grazing. They are likely to choose the most appropriate fields on their farms, rather than tilling steep slopes. It's likely to be a relatively small amount of feed.