That largely depends on where the alfalfa is grown. A lot of the alfalfa grown in deserts is shipped as combination ballast weight for leaving cargo ships and to feed foreign cows and not used for domestic cattle. While nobody around or east of the Great Lakes irrigates alfalfa and is essentially a free product requiring no pesticides and no fertilizer and even adds extra nitrogen fertilizer to the soil. It is just plant, cut, and bail and is otherwise basically a wonder crop for sustainable agriculture anywhere that gets rain once a month or more.

The vast majority of cattle are raised in a pasture and eat grass, even those labeled “grain fed”. Grain fed just means they spend some time (e.g. 30 days) in a feed lot.

I hadn’t heard about cows eating alfalfa though, where is that happening? Wouldn’t it be more valuable to sell it to people instead of using it as feed?