Do we really feed the cows the actual whole soy plant? That sounds incredibly wasteful to me. Or is it just that the parts of soy that we can't eat (stalk, lea

Do we really feed the cows the actual whole soy plant? That sounds incredibly wasteful to me. Or is it just that the parts of soy that we can't eat (stalk, leaves, husks, discarded beans after processing into tofu/milk/etc.) that comprise 80% of the plant, while the rest we consume ourselves?