If you want to discuss this you're going to have to get more specific. What agriculture, where in the world, are feedlots used etc You're obviously excluding aquaculture, and non grazing animals like pigs, I suspect you're also excluding egg production since that is almost monolithically cage farming.
Like you can't really say "oh these pigs are on non arable land" if that merely refers to their physical location and not where their food is grown.
So could you please drill down a bit? what specifically are you referencing?