Tuesday 25 October 2011

Signs Of Cat Inbreeding

Signs of cat inbreeding include the appearance of anomalies, inbreeding depression and a decline in hybrid vigor. I have a page on genetic diseases in purebred cats that shows how inbreeding can affect health. It depresses the immune system and throws up inherited illnesses that are serious.

The cat breeds on the left are the most inbred. The most inbred is the Singapura. The Siberian is the least inbred and on a level of random bred cats. On the far right are 3 subspecies of wildcat. Chart: in the public domain. Click on the image to see it more clearly.


So called "vigor" really means general health and well-being. Inbreeding results in the homozygosity of more genes with harmful effects. Deleterious genes that are carried by cats and which are "dormant" or unseen in physical appearance and health "make their presence felt due to inbreeding".

A classic example is Bengal nose. Breeders, though, would not agree. Breeders tend to downplay inbreeding problems for obvious reasons. And we have the depressed immune systems in modern Siamese cats that results in a depressed lifespan because of general illness that would not be present in random bred cats.

Robinson's Genetics quote the following as examples of possible consequences of inbreeding. More than one may be present or one in the extreme:
  • decline in birth weight - small, thin and lethargic kittens.
  • small litter sizes, more stillborn kittens, abnormal kittens.
  • poor growth in later life and "below standard" individual cats.
  • sterility problems. Poor sperm quality (see wild cat inbreeding), reluctance to copulate.
  • predisposition to illness. One disease kills all the litter.
  • physical deformities or physical appearance that lacks symmetry.
To this list I will add subnormal intelligence. Inbreeding depression can lead, in my view, to individual cats that lack the usual level of intelligence or cognitive function of the typical domestic cat. These cats are noticeable unresponsive and dull in character.

It is my contention that the most established cat breeds tend to have the most established genetic illnesses and the higher number of these sorts of illnesses. Examples: Siamese and Persian.

Purebred cat breeders like to fix a good looking cat persuant to the breed standard by inbreeding. This can also fix a poor immune system.

I have written this on the basis of what I have read over a considerable period of time and in reference to Robinson's Genetics for Cat Breeders & Veterinarians Fourth Edition ISBN 0-7506-4069-3.


  1. For the record, "Bengal Nose" is not related to a lowered immune system, it's thought to be caused by a thinner layer of skin tissue on the nose leather.

    This trait is relatively common in some Bengal lines, but it is not currently known if it is a deleterious recessive or really what its mode of inheritance is.

    1. Hi, thanks for your input. How do you know that Bengal nose is not related to a lowered immune system? Do you have any science to support what you write?

    2. I have a bengal cat with dry "bengal nose" and its extremely common in the breed and has NOTHING to do with inbreeding. Rub alittle coconut oil on it and its brand new, moist and wet and healthy again. My bengal Adelle is extremely intellegent, can open her own cage door, sit, walks on a leash, and is smarter than half the people i know.

    3. How do you know it has "nothing to do with inbreeding"?

  2. This comment has been removed by the author.

  3. Well I guess my cat is inbred.


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