If — and I recognise that it is an "if" given the current lack of any sufficient testable definition of subjective consciousness awareness of self — if farm animals are self-aware, then slavery would be several steps up from their current existence.

We only stopped feeding cows to other cows because of a fear humans might get prion diseases.

Coming at it from the other direction, "what if humans were food?" is a horror trope, be it vampires, zombies, werewolves, or psychopath cannibals.