I did a little more digging regarding water content. By weight dressed chicken is ~60-65% water, so not insubstantial. Dry feed is ~10% water. But even if we do

I did a little more digging regarding water content. By weight dressed chicken is ~60-65% water, so not insubstantial. Dry feed is ~10% water. But even if we double FCR to offset the water weight we're still under 1 order of magnitude, at least for chicken and fish.[1] I think the point still stands. If we consider all the context, such as nutritional needs (can't simply replace all animal protein and fat with processed corn), maximization of diverse agricultural resources, industrial efficiency, relative inefficiencies of whole vegetables and fruits, etc, then some moderate amount of meat consumption is readily defensible. [1] Using other metrics there's a lot of literature that defends beef production, but that doesn't make for good napkin math, and I'm somewhat skeptical of it, anyhow--much of it seems to be published by the beef industry, and if you pick your metric you can make anything look good. Nonetheless, beef production is pretty darned efficient as far as it goes.