Blood that is. Pets need blood too when surgery calls for it. But where do they get that red stuff?
Somebody writing in to the great Cecil Adams' Straight Dope column asked the same question a while back. The answer is: you wouldn't know it, but there are many national, regional and local veterinary blood banks. Your pet can be a donor, though they will get checked over first to see if they are in proper shape to do so. Your vet may have a kitty kicking around the office for company and extra hemoglobin (cats have 3 bloodtypes).
If it's a horse you're helping, the blood may come from Beevo, a horse at Oklahoma State University who happens to be one of the 5% of horses with a universal donor type. Horses have over 15. It gets tricky.
Read the whole answer here, unless you have a hamster, in which case the last sentence will make you pout and I warned you.