How Can We Help?

Search for working dog conference recordings, articles on health, breeding, socialization and organizational management, webinar recordings and more.

Old Conference Archive Page | View all IWDC 2023 Recordings | View all Breeder's Workshop Colorado Recordings


Effective Population Size​

Effective population size (Ne) is a key parameter in population genetics. It is the number of individuals that effectively participates in producing the next generation.  It also quantifies the magnitude of genetic drift and inbreeding within a breeding colony.  The overall goal is to have Ne be as high as possible.  

Note: Although this article is free to read, it contains some resources which are only available to IWDA / IWDR members. Thanks to our members for their support which enables us to create articles and resources like this!

Making Genetic Change with Effective Population Size

There are some key takeaways when using the principles of population genetics for making genetic change.  First, keep a variety of families for breeding, basically begin with least related dogs in the beginning. Then, use selection among offspring of the less related parents to identify those young dogs that are most likely to perpetuate the qualities you desire and keep those young dogs for breeding. Remember to keep a broad cross-section of young dogs across families, so genetic diversity can be maintained.

Second is to have short generation intervals, which will increase the rate of genetic change obtained per year. Use young dogs of the next generation as soon as possible to maintain reproductive capacity and to hasten genetic improvement per year. 

By applying these two key points and doing so by keeping Ne above 20, it is possible for a breed to realize only a slow increase in inbreeding per generation while also practicing selection. Try very hard to avoid matings that produce a rapid increase in inbreeding, which also causes a rapid loss of genetic diversity. Slowly increasing inbreeding over many generations of selection for a set of common goals, will concentrate the “genes” desired to perpetuate in puppies produced as the next generation. It will also ensure the long-term survival of the breed.

When looking at replacement breeders within a family, utilize estimated breeding values (EBVs) to help determine those young offspring that are most likely to perpetuate the goals established for a breed, then optimize matings by identifying mates that complement each other genetically while also producing puppies that are the least inbred.

One of the genetically most devastating moves a breed or breeder can make is to allow one male to sire most or all litters from which the next generation of parents will be chosen. Those puppies might be ideal, themselves, but they are all half-siblings, because they share the same father. This will result in a more rapid increase in inbreeding among puppies born into the next generation. By increasing the number of studs used, the rate of increase in inbreeding can be minimized. This could be accomplished by using frozen semen and/or by allowing males to have dual careers as both a breeder and a working dog. Collaborating with like minded organizations is an ideal way to expand Ne, by exchanging unrelated germplasm or puppies.

Summary Notes on Effective Population Size


  1. Unequal sex ratio of breeding animals
  2. Family size 
  3. Generation interval.



  • Use as many males as you can
  • Utilize Frozen Semen – collect and then repurpose dogs (dual career)
  • Collaborate – get quality unrelated germplasm
  • Turn over generations quickly (Short Generation Interval) & limit the number of progeny from any one individual

Calculating Effective Population Size


Effective Population Size Calculator

This content is for members only. Please login or register to view it.

Was this article helpful?
0 out of 5 stars
5 Stars 0%
4 Stars 0%
3 Stars 0%
2 Stars 0%
1 Stars 0%
Please Share Your Feedback
How Can We Improve This Article?
Table of Contents