(Cedar Hills, Utah, Pleasent Grove)
Do vampires have the ability to chose what blood to drink? Can they chose to drink animal blood vs. human blood?
Yes, vampires can choose to drink animal blood instead of human blood if they choose, though animal blood may not satisfy them completely.
The obvious advantage to drinking animal blood rather than human blood is that it is far easier to acquire. Not only can animals be hunted easily in the wild, but dead animals raise far fewer questions among the human population than dead humans do. Remembering that vampires are best off when not drawing attention to themselves, keeping missing or dead humans off of the radar of the townsfolk is probably a very good idea. Of course, a vampire with a moral code that limits the killing of humans would also benefit from such a diet.
On the other hand, there is a good reason why vampires choose human blood over animal blood for the most part. Human blood replenishes their body cells much better than animal blood does, which is important if your body is technically dead. It's a lot like human vegetarians versus human meat-eaters. You can survive either way, but vegetable proteins do not synthesize as well in the human body as animal meat does, meaning you have to consume more of it to get the same nutritional effect.
It is commonly believed that most vampires feed on humans, but will feed on animals if there is no other options. Of course, vampires have free will and can choose to do whatever they like, but much like our body craves water when thirsty a vampire has a hard time resisting human blood when its body is calling for it.