Comment 109 by Helga Vierich :

*Comment 108 by mysticjbyrd A herbivore is very very inefficient at turning plant matter into energy, And on top of that, the vast majority of that energy is being used to regulates its internal environment(Homeostasis), in other words keeping itself alive. So, if you could simply grow the tissue itself it would be far far more efficient than bringing feed to a slaughterhouse.

Um, no, herbivores are in fact very efficient, compared to omnivores. That is why they are herbivores - they are able to convert plant fibres back into calories, something omnivores and predators did not evolve to be able to do. Certain kinds of totally herbivorous primates (not humans) fall into this efficient category, having special digestive bacterial suites that can deal with plant cellulose.

Maybe we have very different ideas of efficiency. If you mean they are better at digesting plants then we are, then your absolutely right. But, I worked on a farm as well, and I clearly remember putting 10 lbs in one end, and 9 lbs coming out the other end. To me, that's not very efficient.