If you’ve ever donated blood or had surgery, you probably know your blood type, which is determined by two different blood groups, the ABO group and the Rh blood group. The combination of these blood groups determine the antibodies and antigens in your blood, which determine what types of blood can be used for a transfusion in the event that you need one. I, for example, am type O+ (ABO group O and RH group +). One human blood type, O-, is considered the universal donor: anyone of any blood type can receive O- blood and not have a bad reaction.

Your cat has a blood type, too. Although the cat blood typing system is not as complicated as that of humans, it’s very important information if your cat is having surgery or giving birth to kittens. Here are six things you should know about your cat’s blood.

1. Cats have one of three blood types

The cat blood type system is simpler than the human system. Instead of having eight possible types like humans do, cats have three — A, B, and AB. Type A is the most common, occurring in 94 to 99 percent of all domestic cats in the United States, and type AB is by far the rarest.

2. There is no feline “universal donor”

If your cat receives a blood transfusion, the donated blood must be the same type as that of your cat. Otherwise, it can create a potentially fatal reaction in which blood cells are destroyed.

3. Blood type is determined by genes

When it comes to blood types, the gene for type A is dominant — that is, it needs only one copy to express itself. Type B, on the other hand, is recessive, and a kitten would need to inherit type B genes from both its parents to have that blood type. Blood type AB is inherited independently; it appears to be dominant to the B gene but recessive to the A gene.

4. Cat breeding can influence blood type

Blood type surveys of various purebred cats have shown that Siamese, Tonkinese, and Oriental Shorthair cats all have type A blood, perhaps because other types have been bred out, as breeders have selected for certain physical characteristics. On the other hand, the British Shorthair, Cornish Rex, Devon Rex, Exotic, Ragdoll, Turkish Van, and Turkish Angora have an unusually high frequency of type B blood.

Breeds that have are more likely to have the very rare Type AB blood include the Abyssinian, Birman, Bengal, British Shorthair, Scottish Fold, Somali, and Sphynx.

5. Blood type clashes can kill kittens

If cats of different blood types are bred, there’s a chance that at least one of the kittens will have a different blood type than its mother. Because the mom-cat transfers antibodies against blood types in her colostrum (newborn kitten milk), the kittens’ blood cells could be destroyed by the mother’s antigens. According to a paper by the Winn Feline Foundation, researchers believe blood type conflicts could be responsible for a large proportion of “fading kittens.”

6. There are tests that can determine a cat’s blood type

The UC Davis Veterinary Genetics Laboratory has an incredible array of genetic tests for cats, including one that determines blood type. Vet clinics have quick blood typing cards in the event of emergencies, and referral laboratories also offer blood type tests. Many breeders are recording cats’ blood types on their pedigrees in order to prevent breeding cats of different blood types.

For more information about blood types, check out the Fabcats page on the subject or read the entire Winn Feline Foundation page here.

Got any other weird cat science questions? Ask them in the comments, and I’ll (probably) answer them in a future column!

About JaneA Kelley: Punk-rock cat mom, science nerd, animal shelter volunteer, and all-around geek with a passion for bad puns, intelligent conversation, and role-play adventure games. She gratefully and gracefully accepts her status as chief cat slave for her family of feline bloggers, who have been writing their cat advice column, Paws and Effect, since 2003. JaneA dreams of making a great living out of her love for cats.

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