good question. the other day i was talking online witha young man whose dog jumped out of his sisters arms and by mistake hit his chest into the sharp corner of a bureau. he seemed fine. but then he started acting funny in a littel while and they took him to a vet. The vet found the dog, in hitting his chest tore an aorta and was slowly bleeding to death internally. The only way to save him was an operation but the vet said the dog would need a transfusion. The kids' mom said no, as a JW and the dog was put down. Her son did not agree but that was the final decision.
The only use for blood in the bible was for sacrifice, otherwise (animal or human) it would be poured out on the ground.