I don't know how that would work out, but I doubt it would be any less efficient. An awful lot of energy in animal-rearing goes into building parts of the creature that don't get eaten (especially in larger animals) - bones, brains, viscera, skin and so on. Only a relatively small part of the animal is actually getting eaten, so even if the energy density of the meat is enough to make up for the wasted energy in producing it [citation needed] the wasted energy accrued in the products that never get eaten would probably eliminate any gain.
It would be possible to eat meat more efficiently than we do by increasing the scope of the meat sources we were prepared to consume. Hence why I got annoyed at PETA earlier in the thread for their "pet food is made from offal - shock horror!" There's nothing wrong with eating offal, and people can - and probably should - eat more of it. It's just that an overabundance of lean steak meat and a general modern cultural feeling that offal is "icky" means that most people don't.
Indeed, but domestication has led to a massive increase in numbers of those species. In the numbers they lived in in their wild state, they weren't causing such a problem. Even if we don't exterminate domestic species in a quest for vegetarianism, any reduction in numbers of those animals would benefit greenhouse emissions.I have seen the numbers on the emmisions of the livestock, but that's a natural biological emission. If that animal had never been domesticated and was roaming free in the various plains and praries they'd be putting out at least similar if not the very same amount of green house gasses. Eliminating that emission is calling for that animal to be driven to extinction.
I expect you're right.I'm pretty sure you can't get all of the necessary vitamins and nutrients necessary to maintaining peak health from only fruit...