Factory farms help with the numbers. You can keep pigs more dense even if they don't depend upon the area for the source of feed - just like humans and urban de

Factory farms help with the numbers. You can keep pigs more dense even if they don't depend upon the area for the source of feed - just like humans and urban density. A high density in 1 acre ks perfectly plauisble but it ignores the feed crop acres. At that point efficency should be total crop calories * pig efficency margin (10% for standard trophic level to back of the envelope) / (acres of corn + acres of pig). If you took the density scale to something really absurd the pig acre efficiency would be the crop times the multiplier as that space converges eventually converges to becomes negligible and just "pig efficency * feed crop calorie/acre" effectively. Granted the effective convergence point may not be realistic without real world data but if factory farms are big enough it comes out to the same order of magnitude as brocoli about 1.5 vs 2. Of course there are a lot of other things to legitimagely object to about said arrangement but it surpringly lines up to be comparable to vegetable crops in caloric efficiency. A more in depth answer would look at the caloric share of diets in consumption - most people don't get their bulk calories from vegetables.