Blood groups and blood group incompatibility

Like many other traits, blood groups are inherited in cats. The blood groups that occur in cats are "A", "B" and "AB". Knowing the blood group of your own cat can be vital in case of a necessary blood transfusion and/or when breeding.

Distribution of the different blood groups

Blood group "A" is the most common (about 73%), blood group "B" about 23%. The rarer blood group "AB" occurs in only about 6% of all cats.

Breeds that often have the blood group "A" are for example: Devon Rex, European Shorthair, Exotic Shorthair, Norwegian Forest Cat and Oriental Shorthair. According to statistical evaluations, cats of the breeds Russian Blue, Turkish Angora and Turkish Van also very often have blood group "A".

The blood group "B" is more or less frequent in the following breeds: Abyssinian, Birman, Maine Coon to about 1-10%, Persian and Somali to about 10-20% and British Shorthair, Carthusian, Ragdoll to about 20-35%.

Cat breeds with blood group "AB" are for example Abyssinian, Birman, Somali, British Shorthair (1-5%) and Persian and Ragdoll (6-15%).

How are blood groups inherited?

Just like all other hereditary traits, the blood groups of a cat are determined by the inherited genetic information of the parents. The blood groups are passed on to the offspring in a dominant-recessive inheritance, with blood group "A" being dominant to the other two blood groups. Blood group "AB" is recessive to blood group "A", but dominant to "B", resulting in a dominance sequence of "A"

> "AB" > "B".

Pure and mixed heredity in blood groups

The genetic make-up of a living being is determined by the hereditary information passed on by its parents. A kitten receives half of this information from its mother, the other half from its father.

The information can be different or the same. If both pieces of information are the same (for example, both parents pass on the blood group "A"), one speaks of "pure heredity" with regard to this information. If both parents pass on different information (father: blood group "A", mother: blood group "B"), this is called "mixed heredity".

Blood group "A" can be both homozygous ("A/A") and heterozygous ("A/B", "A/AB"), as can blood group "AB" (homozygous: "AB/AB", heterozygous: "AB/B").


The dominant-recessive inheritance in blood groups

Certain traits in heredity are dominant (= prominent), others are recessive (= regressive). Dominant traits cover recessive traits in mixed heredity. Recessive traits only appear externally if they are homozygous. They must therefore be present twice in the genetic blueprint (passed on by mother and father) in order to be visible externally.

Recessive traits can be carried covertly without showing. They are passed on to the offspring without having to be visible. Dominant traits also always show themselves externally.

The blood group "B" can only show itself in a pure form, because as a recessive trait it is suppressed by the dominant blood groups ("A" and "AB") in the case of mixed heredity.


Inheritance of blood groups "A" and "B

A mating of two homozygous animals with blood group "A" will only produce kittens with blood group "A". If one or both parents are heterozygous for blood group "A", the kittens will also have blood group "A".

In a mating of a homozygous animal ("A") with a partner of blood group "B", the kittens receive the dominant blood group "A". Kittens receive half blood group "A" and half blood group "B" if one parent is homozygous to blood group "B" and the other parent is heterozygous to blood group "A" ("A/B").

The mating of two animals with blood group "B" produces exclusively kittens with blood group "B".

Blood groups of the parents

Blood group of the kitten

A/A x A/A

Blood group: A

100%: homozygous (A/A)

A/A x A/B

Blood group: A

50%: homozygous (A/A), 50%: heterozygous (A/B)

A/B x A/B

Blood groups: A and B

25% homozygous (A/A), 50%: mixed (A/B), 25% homozygous (B/B)

A/A x B/B

Blood group: A

100%: Mixed (A/B)

A/B x B/B

Blood groups: A and B

50%: homozygous (B/B), 50%: mixed (A/B)

B/B x B/B

Blood group: B

100%: homozygous (B/B)


Inheritance of the blood group "AB

If a homozygous animal with blood group "A" is mated with a homozygous or mixed blood group "AB" partner, the kittens will have the dominant blood group "A". Kittens resulting from a mating of a mixed-blood animal (blood group "A") with a homozygous partner of blood group "AB" have half blood groups "A" and half "AB".

A litter with all three blood groups is produced when both parents are heterozygous and have the blood groups "A" and "AB". Two purebred parents with the blood group "AB" can only pass this on to their kittens.

Further possible combinations can be seen in the following table.

Blood groups of the parents

Blood group of the kitten


Blood group: A

100%: Mixed A/AB

A/A x AB/B

Blood group: A

50%: A/AB, 50%: A/B, all mixed


Blood group: A und AB

50%: A/AB, 50%: AB/B, all mixed

A/B x AB/B

Blood group: A, AB und B

25%: A/AB, 25%: A/B, 25%: AB/B, 25%: B/B, homozygous and mixed


Blood group: AB

100%: homozygous (AB/AB)


Blood group: AB

50%: homozygous (AB/AB), 50%: mixed (AB/B)


Blood group: AB und B

50%: mixed (AB/B), 25%: homozygous(AB/AB), 25%: homozygous (B/B)


Blood group: AB

100%: mixed (AB/B)

AB/B x B/B

Blood group: AB und B

50%: homozygous (B/B), 50%: mixed (AB/B)



What is blood group incompatibility? How does it develop?

The cell surfaces of the red blood cells are different for the different blood groups. Since the body produces antibodies (called "alloantibodies") against the other blood groups, the red blood cells can dissolve or clump together when the different blood groups mix.


Blood transfusions and blood group incompatibility

Not only at birth and rearing should the blood group of all cats concerned be known in order to prevent blood group incompatibility. Also before blood transfusions it is enormously important to find out the blood group of the donor and the recipient animal. If the "wrong" blood group is administered to the recipient animal, this can lead to damage and death. In the meantime, quick tests to determine the blood group are also possible (see How do I determine the blood group of my cat?).


What is "fading kitten syndrome"/"Feline Neonatal Isoerythrolysis"?

Fading kitten syndrome" or "Feline neonatal isoerythrolysis" is the name given to the incompatibility reaction of the blood groups.

In this case, the blood cells of the kitten are destroyed by the alloantibodies of the mother's blood group. This can lead to a wide variety of symptoms in the kittens: from the death of some parts of the body to an agonising death.
What symptoms do affected kittens show?

If a mother cat with blood group "B" has a litter consisting of "A" kittens, health problems may occur. However, problems do not always have to occur with such a combination. The decisive factor is the concentration of the mother's alloantibodies (see "Have antibody concentration / titre measured").


How can I prevent kitten death?

First of all, it remains to say that such a problem can be avoided in advance if the blood groups of male and female cats are known before mating and corresponding knowledge in genetics is available to be able to assess the risks and advantages against each other.

If kittens are born at risk, care should be taken at birth and in the first days of life. The intake of the first mother's milk should be avoided and the kittens should be hand-fed in the first two days of life to prevent damage and mortality to the kittens. It is also possible to let the kittens suckle in the first time by a suitable cat midwife.

Have antibody concentration / titre measured

Not every cat with blood group "B" has strong antibodies against the other blood groups. The concentration of these antibodies in the blood varies greatly. There are cats whose antibody concentration only causes weak intolerance reactions.


How do I determine the blood group of my cat?

There are different tests to determine the blood group of a cat. On the one hand there are quick tests (test cards), genetic tests and on the other hand tests of the blood serum.

Which cats can I safely mate with each other?

Cats with the blood groups "A" and "AB" can be mated with males of all blood groups without any complications. Also males with blood group "B" can mate with all cats.

More information on the inheritance of blood groups can be found in the section "Genetics in cats - Inheritance of blood groups").


What are the risk matings with regard to blood group incompatibility?

A cat with blood group "B" should only be mated with a "B" male, as complications are possible with all other blood groups ("A/A", "A/B", "AB/AB", "AB/B") (see table "Inheritance of blood groups").


Which blood groups are found in cats and how are they inherited?

There are three blood groups in cats: "A", "B" and "AB", whereby the latter is extremely rare. Blood group "A" is dominant, i.e. it prevails over both blood groups. Blood group "B" is recessive and is only "shown" if both parents pass it on to their kittens. An animal that "shows" blood group A can be either homozygous ("A/A") or heterozygous ("A/B"). The blood group "AB" is a speciality and arises when the dominance of the blood group "A" is eliminated by an additional special hereditary information and "A" and "B" mix equally. The blood group AB can also be purely hereditary ("AB/AB") and mixed ("AB/B").

Blood group "AB" is recessive to blood group "A", but dominant to blood group "B". In the order of dominance, the blood groups would therefore be: A >AB> B.


Inheritance of blood groups in cats

How the inheritance of blood groups is statistically distributed in cats is shown in the following table (as blood group A is dominant, it is highlighted here in bold):


Inheritance of blood groups

*see "Heredity and blood group incompatibility".

 Result: If a homozygous parent ("A/A", "AB/AB" or "B/B") is mated with a heterozygous animal ("A/B", "A/AB" or "AB/B"), half of the offspring will receive the blood group of the homozygous parent, the other half will be heterozygous and will receive the dominant blood group ("A" or "AB"), but will also recessively carry the hidden blood group ("B" or "AB").

If two purebred parents pass on the same blood group to their kittens, all resulting kittens will receive this blood group. If two homozygous parents pass on different blood groups, the kittens will be heterozygous and will receive the dominant blood group, but will also recessively carry the hidden blood group.