But the reality isn't like that. Something that sounds so horrific can be a good thing.
Animals need blood when they suffer trauma or blood poisoning. And some local veterinarians keep animals around their offices just for that reason. At the Guardian Animal Hospital, a black cat called B.D. serves as the resident blood donor.
B.D. came to the clinic about eight years ago. Then a kitten, she had been caught in the fan belt of a car, Dr. N.J. Wixsom said. A veteran blood donor, she has given blood three times in a three month span, and gone some years without giving at all.
A new chemical product called hemoglobin-glutamer-200 has reduced the need for red blood cells, Wixsom said. It's a store-at-room-temperature product that carries oxygen through blood vessels.
But veterinarians still need live donors if they need fresh plasma or platelets, she said.
Wixsom uses a kit to draw blood from the jugular vein and put it into a bottle or a plastic bag much like the American Red Cross uses for human blood.
The blood must be mixed with an anticoagulant to prevent clotting and glucose to make it stable enough to transfuse, Wixsom said.
A typical cat can give only about 50 to 75 milliliters of blood at a time -- about 2 ounces, Wixsom said. An average dog can give about 500 milliliters.
Most dogs can give blood without sedation, Wixsom said, but most cats can't.
B.D. receives a light sedation, enough to make her very cooperative. She has no claws, but still has her teeth.
Without sedation, Wixsom said, the staff would get blood, but it would be theirs.
Like 97 percent of all cats, B.D. is a domestic shorthair. The same percentage of cats have type A blood.
Dogs have a wider variety of blood types, Wixsom said.
Greyhounds make the best blood donors because they have a higher amount of red blood cells per volume. They also have easy-to-find blood vessels.
Wixsom's own dog, Isaac, a Labrador retriever, donates blood about two or three times yearly. He knows when it's coming.
"Isaac starts to shake the instant we put him on the table," Wixsom said. "He's like, 'Mom, not again."'
At the Ashland Animal Clinic, Dr. David Pinkston's dog, Grace, does the honors. She doesn't mind being stuck, receptionist Tanya Meadows said.
"It's getting her up on the table that's hard. That, and the word 'bath,"' Meadows said. "She usually knows that something's up when Dr. Pinkston calls her."
Grace has a free rein in the clinic, along with an orange-tinted cat named Ralphie. Ralphie attacks bigger dogs in the lobby and playfully bites the chins of people who hold him.
The staff hopes that one day Ralphie, who's about 6 months old, can become a blood donor too.