Notes on inbreeding depression.
This is something that happens in nature as well as in the cat fancy. Cheetahs - and I am not talking about captive cheetahs - are inbred due to an event that happened a very long time ago. Siberian tigers are inbred causing reduced fertility. This is due to low populations in two island zones in the far east of Russia. White tigers at zoos are great to look at provided you don't know about the inbred malformations that some white tigers suffer from due to irresponsible breeding.
The inbreeding depression that interests me more currently is that which is inadvertently encountered by purebred cat breeders in their desire to achieve a desirable trait and to fix it. By this I mean to create a cat that looks fantastic and which fully complies with the breed standard.
Inbreeding depression reduces the ability of a species to survive. It results in low fertility and a weakened immune system. Inbreeding brings together harmful recessive genes that have been hidden for years. When two recessive genes come together (homozygous condition) they become active and express the trait that they can create.
Long standing cat breeds such as the Persian and Siamese have longer lists of genetic diseases than the other breeds. Bengal cats have been created from very few foundation cats. "It is estimated that over 37% of Persians have PKD1 (Polycystic Kidney Disease), a breed that accounts for nearly 80% of the cat fancy." How prevalent is HCM (a heart disease) in Bengals and Maine Coons (more on that soon...)?
I won't go on - I could. I am not "breeder bashing" just telling some people that it is advisable to look behind the fluffy and fantastic.
Breeders should be very, very careful about inbreeding and line breeding. The desire to achieve a desirable trait should be tempered with caution and knowledge. To be blinkered by the desire to win at cat shows can result in cats that are inherently unhealthy with poor immune systems and susceptible to disease.
Genetic diversity should be the first call of a responsible cat breeder. Appearance comes second. Unfortunately this is not always the case.
Cat show awards should be qualified by the cat's health and not be solely based on appearance. That does not happen currently.
Cat Inbreeding to Home Page