I'm not even sure how this is supposed to be an argument.
It might be valid if coming up with the amount of feed necessary was a problem, but it's not.
You could also make the same argument about plants; that they take in way much more energy in sunlight than they output when being eaten. What would you suppose we do to that, inject chloroplasts into our cells?
It's a very stupid point.
Energy isn't going to be conserved in any organism to a massive extent.
Animals have to respire and move and do metabolic processes.
The energy you put in to them goes into growth, alongside those factors.
If it didn't go into those factors, the animal would die and you wouldn't eat it at all.
Irishbandits points are all stuff.
There's plenty of land on the planet for breeding animals. I live in the countryside in England and approx 95% of all land here is used for fields.
Not all of those are used as farms for livestock or plants either.
Just because cheap farms in South America and Africa are cutting down rainforests to breed livestock doesn't mean those are the only locations we could breed them.
Who knows what the future could hold anyway. With the advent of cloning of meat, we might simply need laboratory factories to produce 100% meat.
And the point about stomachs is just stupid.
Human stomachs are designed to eat meat. We are an omnivorous species. If you fill the forgeter with beef, then it won't go down too well.
But that's the case with anything.
