You don't keep the animal alive indefinitely in a questionably vegetative just to grow up its organs though - you let it roam about (likely in a caged and germ

You don't keep the animal alive indefinitely in a questionably vegetative just to grow up its organs though - you let it roam about (likely in a caged and germ free, granted, but hopefully large, facility) and when the time comes to harvest the organ, you sacrifice the animal in a humane way.