Genetics Course 1

Effective population

”The inbreeding effective population size does not measure the number of dogs used in breeding.
What it measures is the rate at which a race of animals loses genetic variation. “ (Per-Erik Sundgren) 

- Inbreeding effective population size has nothing to do with how large in number of dogs a breed is.

 - Inbreeding effective population size has nothing at all to do with the number of dogs in a breed actually being used for breeding.

 - Inbreeding effective population size points to one thing only: how fast genetic standardization grows within that breed.

 -Inbreeding effective population size is given as a number: e g,50, 100, 200 or 500.

But that does not mean that 50 dogs are used for breeding purposes within that breed, or that 500 dogs are bred from.

It does mean that the genetic standardization of the breed proceeds as quickly AS IF  there were only 50 animals – 25 dogs and 25 bitches – to breed from.

Or that the genetic standardization proceeds as slowly AS IF all of 500 dogs were being bred from.

Why would this be so very important to know for everybody who wants to breed animals with a closed stud book?

That´s easy! With an effective inbreeding population size of 500, there is such a tiny loss of genetic variation for every new generation of dogs that the breed can go on for a very long time and not have defective genes build up and starting to show. One rare  dog here and another one there will have the defective genes doubled and in consequence will suffer from genetic disease. But the breed as a whole remains healthy!

With an inbreeding effective population size of 50, the breed will lose so much of its natural genetic variation that defective genes  will build up and start to show. Many dogs have doubled defective genes and are affected.  Many of the rest are carriers. And the breed as a whole is no longer healthy.

Inbreeding effective population size is as simple as that. You don´t have to be a geneticist to understand it.

The first obligation of breeders of purebred dogs is to maintain the inbreeding effective population size. All the rest – the defective genes, the dominant and recessive traits, the genetic diseases – can safely be left to vets and geneticists. They handle these things well. It´s their job.

Breeders and breeders alone can answer for the effective population size.
And keeping it substantial is THEIR job!