>not every place in the world is suitable to the sort of cropping required.
That would be relevant if the livestock were grassfed but in the modern world where Soybeans from brazil are shipped to UK to feed cattle or From USA to Australia to feed pigs that doesn’t seem to be a problem.
Soybeans is pretty much one of the best crops for feeding animals because it fixates all the nitrogen it needs, unlike 95% of other grain crops. The only thing more efficient to grow fertilizer wise is alfalfa, which is what most cows are fed, but would not be any good for feeding pigs or chickens because it is hard to digest like grass.
What most people tend to forget is the scale of factory farming. About
30,000,000 cows 130,000,000 pigs and 8,000,000,000 chickens are killed yearly in the US alone. You can imagine that they cannot be just grassfed besides the fact that pigs and chickens do not eat grass so they are fed soy that could fed to humans, animals are not magic machines that turn air into food, the only thing capable of converting nitrogen water and sunlight into protein are plants, any step in the middle generate loses, animals need energy for their vital processes so the rate of conversion of fed-to-edible calories is aprox. Poultry:11% pigs:10% Beef:1%
(I could cite the sources if anyone wish to investigate more)
All this is just the efficiency aspect of it, let’s pretend they don’t need water or create any waste.
That would be relevant if the livestock were grassfed but in the modern world where Soybeans from brazil are shipped to UK to feed cattle or From USA to Australia to feed pigs that doesn’t seem to be a problem.