Humans only eat the beans, because those are a valuable protein source. Actually, it's one only very few practical, mass produceable vegan protein sources. Cat

Humans only eat the beans, because those are a valuable protein source. Actually, it's one only very few practical, mass produceable vegan protein sources. Cattle, can also digest the rest of the plant. Like they would digest grass. And if you have the stuff anyway, why not feed it to grow some cattle meat. However, for high performance, that ain't enough, you still need more protein. Soy protein is an important and (so far) cheap protein source in many animal feeds. But it is getting more expensive and problematical...