There is a brilliant insight here: the free will of animals other than the human. All animals have free will whether we human animals care to acknowledge that or not. They do make choices, which are concrete demonstrations of free will. They choose to be content with their natural lives. When faced with a stun gun and meat cleaver, or a skinning knife, or a bullet, or an arrow, or a hook, or a pot of boiling water, or a harpoon, or a corral, or a cage, or a tether, or any weapon or means of confinement, they choose to get away. Simply because human animals disallow their escape or take advantage of their vulnerability does not negate their having made a choice.

If you look into an animals eyes, any animals eyes, you can tell which choice they have made.
Disallowing that choice is the definition of barbarism.