Here's a great explanatory model...

Well, ol' Ray has outdone himself again with this stunning illustration of how cows process plant material into substances more easy for humans to digest. Check it out. Read his text too, just so you know that I'm not misrepresenting him. It's wild that he's trying to turn an extremely well-understood biological process into a magical mystery.

By the way Ray, humans are awesome at turning biological inputs into milk. We're mammals. :-D