Vampires search for animals to leach blood from.
There are several problems:
You cannot restrict the setting to only leech from tame animals.
Setting it to leech some blood but not to death will cause the vampire to go out and find wild animals and leech a bit and then engage them in a fistfight (!) he even does it with very dangerous hostiles like dangerous herd animals that will group attack him and kill him easily.
Also a Vampire killed a prisoner when he should only leech non lethal.
Vampires search for animals to leach blood from. There are several problems: You cannot restrict the setting to only leech from tame animals. Setting it to leech some blood but not to death will cause the vampire to go out and find wild animals and leech a bit and then engage them in a fistfight (!) he even does it with very dangerous hostiles like dangerous herd animals that will group attack him and kill him easily.
Also a Vampire killed a prisoner when he should only leech non lethal.