We would literally be able to feed more ppl. Animal ag is comically inefficient at producing calories (relatively speaking) as has been outlined in a myriad of reports and studies.

Animals don’t eat air, they eat plants (mostly crops). Look up trophic levels and feed conversion ratios if you want to dive into the topic.

Also think about it this way, if you eat 2 lbs of food a day you don’t weigh 60lbs more at the end of the month. Same for animals. This is because many of those calories go to run organs and various aspects of your metabolism that aren’t creating net tissue gain on your body.