 -- A sick cat in Florida got a lifesaving blood transfusion from an unlikely donor: a dog.

Buttercup is now recovering at home after the procedure at Marathon Veterinary Hospital in the middle Florida Keys last month. Dr. Sean Perry, who performed the transfusion, told ABC News that cross-species blood transfusions, called xenotransfusions, aren't common in veterinary medicine but are an option in certain cases.

"It would have taken at least 24 to 48 hours to get cat blood," Perry said.

Buttercup didn't have that much time, but the veterinary hospital had donated dog blood on hand.

Cats and dogs, like humans, have different blood types, Perry said. But dogs have a universal donor blood type and are larger, so their blood is more often available at animal blood banks.

"We try to stick to species-specific [transfusions]," Perry said. "But because Buttercup's blood volume was so low, we were able to use dog blood instead of cat blood."

Buttercup's owner brought him in to the hospital after noticing his pet was "very lethargic, not wanting to get up, not wanting to walk around," Perry added.

The cat is recovering but still visiting Perry for checkups.

"Buttercup is at home and doing quite well," Perry said. "What we try to do with transfusions is buy some time in order to get Buttercup's bone marrow to kick into gear. Buttercup has developed red cells of his own now."

The hospital still does not know what caused Buttercup's red blood cell levels to drop.