MOST INBRED CAT BREEDS
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.
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.