There are 3 different feline blood types: A, B and AB

Studies have shown that the A and B alleles are situated on the same locus. For the AB blood type, studies have recently proved the existence of a third allele, the “ab” allele.
ab and b are dominated by a and b is dominated by ab
Thus: a > ab > b

 

A cat whose blood type is A will therefore be: aa, aab or ab
A cat whose blood type is AB will be ab ab or ab b
And finally a cat whose blood type is B will inevitably be bb

Breeding a blood type A cat with a blood type B cat can sometimes lead to a stillbirth.
When a female blood type B cat had blood type A kittens, the kittens may suffer from a haemolytic neonatal disease: MHN.

With certain breeds, the prevalence of the B blood type is such that matching the future parents’ blood types is highly recommended. You can do it yourself with kits that are available to buy through Alvedia ( http://www.alvediavet.com). Certain private laboratories and veterinary schools may also do blood tests.

MHN risk table, depending on the union
 

	Male A	Male B
Female A	0	0
Female B	MHN	0

 

This is a theoretical table, with certain breeds there are fewer problems than you would expect. In some cases, blood type incompatibility only manifests itself through necrosis, the end of the tail or tips of the ears for example. The kittens then have no further health problems.

Breeders who are aware of the risks that could befall the kittens of a blood type “B” female bred with a blood type “A” male separate the kittens at birth which stops drinking of colostrum which a high amount of antibodies. The kittens are then returned to their mother after 36-48 hours.

The kittens are at risk not only because of the high amount of antibodies in the colostrum, but also due to the high permeability of their intestines which let the antibodies through.

There are other blood components that come into play with regards to blood incompatibility but studies have not yet revealed what these components are.

The b allele being very common in Devon Rexs and British Shorthairs, the risk of MHN is about 25%. It is 18% with Persians and 14% with Birmans.
Allele b allocation in different pedigree cat breeds:

Siamese, Burmese, Tonkinese -> close to 0
Maine Coon, Norwegians -> inferior or equal to 5%
Abyssinians, Japanese Bobtails, Persians, Somalis, Sphinx, Birmans -> between 5 and 25%
British, Exotic Shorthairs, Cornish and Devon Rex -> between 25 and 60%
The AB type allocation is insignificant and therefore unknown.
When doing a blood transfusion, blood tests and matching must always be done beforehand.
Transfusions must always be carried out from type A to type A, type B to type B and, if possible, from type AB to type AB. In the absence of a type AB blood donor, it is possible to give an AB blood type cat type A blood.

A. Brisson 09/01/03 reviewed 06/02/09