There are many pets available today that experts recommended feeding (infrequently or at times solely) on live animals. Many reptiles (snakes, chameleons, geckos, monitors, etc.) and many fish are recommended to be fed live animals.
In the UK it is illegal to feed live mice/rats/rabbits/chickens to animals such as snakes but allow the feeding of live insects in any event. In countries where this law doesn't apply would it be muttar to feed a mouse to a snake or a cricket to a gecko regularly?
These animals would be considered sheratzim which may make this a null question in any case! What about non-sheratzim, like feeding live fish to a bear at a zoo?