I did know about grain being used to feed cattle, but a lot of the grain they eat is not of "human quality" so saying that we can just switch humans from meat to grain and feed 800 million people is very misleading.
1) the vast (vast) majority of corn consumed by humans is processed into things like corn syrup, modified starch, whiskey, etc, rather than eaten "whole" as a grain [like, say, as tortilla chips or whatever], so the notion of broken kernels, etc, scarcely applies to this particular consideration -- see above-linked infographic
2) The question of what type of corn is grown is a really interesting one -- I could rattle on about this for a long time, but suffice to say that the family of varieties generally known as "Corn Belt Dent" [derived at some length from Nothstine and similar early dent corns] is designed to serve both feed / silage and processing-for-human-consumption [including ethanol] purposes. Now, this is not stuff you eat as "corn on the cob" [those are called sweet corns, though back in the day folks used to eat green Corn Belt Dent roasted as "Trucker Ears"], nor is it the same as popcorn [which is its own family, derived at length from flint corns]. There are in fact varieties designed specifically for silage [the common type of feed, where pretty much the entire plant is fermented and fed to animals; these varieties have less fibrous leaves and sometimes more leaves] and grain / processing / ethanol ['floury' types], but it's a matter of choice / market analysis from the farmer's perspective, and ye olde corn belt dent can serve both purposes if need be.
one quick link re : ethanol : https://articles.extension.org/pages/27536/corn-for-biofuel-...
> We're not talking about fundamentally different plants, just the difference between seeds, stalks, & husks vs seeds alone.
I think it's also how its stored and # of broken kernels (for corn anyways), etc.
Im not arguing against the point, was just trying to bring some perspective