What the commenter probably refers to is the fact that grazing animals eat plants which humans can not eat while vegetarians eat those which are suitable for hu

What the commenter probably refers to is the fact that grazing animals eat plants which humans can not eat while vegetarians eat those which are suitable for human consumption. The grass eaten by herbivores 'just grows' while the cabbages, lettuces, beans and sprouts (et al) eaten by vegetarians (et al) don't "just grow", they need to be grown purposefully on soil which has been fertilised, they need to be protected from insects and vermin, etcetera. Had the herbivores been harvested from the wild this would all be true. In practice the herbivores are fed not just grass but beans, grains and other produce. Which has to be grown just like the vegetables eaten by vegetarians. Since the 'conversion factor' - the efficiency by which an animal transforms 1 kg of fodder into 1 kg of edible animal - varies from about 2 (insects) via 5-7 (chicken) via 9-11 (pig) to 14-18 (cow) it becomes clear that it takes a lot more grains, beans and such to feed a carnivore than it takes to feed a vegetarian.