spike proteins digested like any other proteins (hence destroyed)

I wouldn't be too sure of that. If the spike protein is like the prions of mad cow/Creutzfeldt-Jakob disease, cooking won't do anything, the meat will still be infected.

about killing the livestock (probably like humans, not all of them, but enough to cause hardship, raised prices, fear, etc).

Oh, without a doubt, that's part of it.

an oral one that would NOT be destroyed by digestion nor broken down/disseminated as in an animal

That's truly disturbing.