This idea is quite simple.
Being able to release an animal back into the wild.
It would mean that after clicking the option on a cow, pig, or sheep, that in 10 or so minutes they return to their wild state.
After returning to their primal state, they would either despawn if no one is around, or be able to attack, like with pigs.
This could be utilised to create armies of beasts without new AI coding, etc.