I eat alfalfa too, and sell some in my shop. But neither me or the cows eat only that: we like to diversify our intake to stay healthy and (global or local) logistic bring us a variety of other food/nutrients.

Sure some cows eat more alfalfa than me but most of them never taste a bit of that and only knows corn, soy and friends.

Some other superplants in the soy/quinoa category to consider: buckwheat and lupinus. Yummy.