Without disagreeing with any of the points I will say that much of the beef that consumers eat are being feed things that are not quite as wholesome sounding as grass grown by the sun. I know a man that help a friend feeding cattle and waste from a neighboring chicken farm was involved (legally somehow).
I agree completely, but I was striving for an ideal in contrast to what we got out of the veggie burger people so far.
As an aspiring farmer, I know that chicken poop is prized for its high nitrogen content, and that energy content combined with a cows digestive system, might make it a source of food on a technical basis.
Its because a chicken is a bird, and birds digestive systems are not designed to extract nutrients completely, they are designed to be light enough to fly and extract them quickly and eject.
That said, as an aspiring farmer, my cows will get the sun grown grass and whatever supplements I would eat myself. :|
The chicken poop is useful in the vegetable or fruit gardens, no problem.