By Carol Beuchat PhD
Using Crossbreeding to Address Inbreeding and Genetic Diversity in Dog Breeds
Effective genetic management of animal populations relies on several breeding strategies, including inbreeding, outcrossing (within a breed), breed crossing, backcrossing, grading up, and rotational breeding. Among these, crossbreeding is particularly useful for creating new breeds and solving genetic problems like excessive inbreeding and loss of diversity.
For dog breeders, crossbreeding is an essential tool for improving genetic health. However, it requires a different approach than routine breeding within a breed. To ensure success, breeders should carefully plan their strategy before starting. Here are some key factors to consider:
1) What problem are you trying to solve?
In purebred dogs, two major genetic concerns are inbreeding and loss of genetic diversity. These issues can lead to increased health problems, reduced fertility, and shorter lifespans. While other traits such as behavior, size, disease risk, or longevity are important, many of these are linked to inbreeding and diversity loss. The best way to improve these traits is to first address genetic health at the population level.
Effective genetic management of animal populations relies on several breeding strategies, including inbreeding, outcrossing (within a breed), breed crossing, backcrossing, grading up, and rotational breeding. Among these, crossbreeding is particularly useful for creating new breeds and solving genetic problems like excessive inbreeding and loss of diversity.
For dog breeders, crossbreeding is an essential tool for improving genetic health. However, it requires a different approach than routine breeding within a breed. To ensure success, breeders should carefully plan their strategy before starting. Here are some key factors to consider:
1) What problem are you trying to solve?
In purebred dogs, two major genetic concerns are inbreeding and loss of genetic diversity. These issues can lead to increased health problems, reduced fertility, and shorter lifespans. While other traits such as behavior, size, disease risk, or longevity are important, many of these are linked to inbreeding and diversity loss. The best way to improve these traits is to first address genetic health at the population level.
| 2) How do you choose which dogs to cross to? Many breeders want to start by selecting a breed for crossing, but a purebred dog breed is probably not the best option. The focus should be on reducing inbreeding and increasing genetic diversity, goals that can be difficult to achieve by crossing with another purebred breed. Why? Because most purebred dog breeds already suffer from inbreeding and reduced diversity. If you cross your breed with another inbred breed, all of the offspring will inherit the same allele from every homozygous locus. This produces a population of F1 dogs that will all have the same allele at every locus that was homozygous in either parent, making inbreeding a potential problem again after the first generation. |  |
Instead, consider landrace dogs or breeds that are not bred to a strict standard in a closed gene pool. There are about 200 recognized breeds in the UK and US, but hundreds more from around the world, some formally recognized,and some not. Check out Desmond Morris' excellent book, Dogs, which describes over 1,000 dog breeds.
To maximize genetic diversity, look for dogs that:
✔ Have low inbreeding and high genetic diversity
✔ Come from populations that have not been selectively bred to conform to a strict standard
✔ Have escaped kennel club recognition, such as landrace or working dogs
✔ Can be DNA-tested to confirm desirable genetic diversity
Choosing diverse, genetically healthy dogs as outcross partners creates a stronger genetic foundation for future breeding.
To maximize genetic diversity, look for dogs that:
✔ Have low inbreeding and high genetic diversity
✔ Come from populations that have not been selectively bred to conform to a strict standard
✔ Have escaped kennel club recognition, such as landrace or working dogs
✔ Can be DNA-tested to confirm desirable genetic diversity
Choosing diverse, genetically healthy dogs as outcross partners creates a stronger genetic foundation for future breeding.
3) How should you think about traits?
Your focus in a crossbreeding program should be on genetic diversity, not specific traits.
Why? Because trait selection requires genetic diversity. You can’t select for particular traits if the necessary alleles aren’t present. By introducing new diversity, you are building the genetic foundation needed to re-establish breed traits later.
Also, keep in mind that genetic health is more than just managing disease mutations. Many traits, including immune system function and adaptability, rely on complex genetic interactions. Focusing too soon on specific physical traits can limit genetic progress and reduce the overall health benefits of crossbreeding.
Remember that for polygenic traits, F1 puppies will get a random collection of only half the alleles of the parent used in the cross. It’s unlikely that a puppy will inherit all of the variants involved in a complex trait. Again, focus on capturing maximum genetic diversity, then you can use focused selective breeding to shape traits with the most diverse genetic pantry possible.
4) What about genetic disorders?
Every animal carries recessive mutations, but these typically do not cause disease as long as the locus remains heterozygous (i.e., one normal allele is present). Recessive mutations become a problem as a result of inbreeding, which produces homozygosity. The key to good physical health is low inbreeding is supported by high genetic diversity.
Trying to reduce genetic health disorders by eliminating recessive mutations from the gene pool is difficult (you need to find every last recessive mutation) as well as genetically destructive, because selection against mutations will work against your goal of protecting genetic diversity.
A more effective approach is to:
✔ Focus on maximizing genetic diversity and avoiding inbreeding to reduce the risk of harmful mutations becoming homozygous
✔ Recognize that many disorders are complex or polygenic, meaning we don’t always know which genes are involved
✔ Avoid extreme selection pressure that could narrow the gene pool further
The safest way to minimize risk from inherited disorders is to restore a healthy genetic foundation first.
5) How should backcrossing be handled?
Restoring breed type after a crossbreed introduction often involves backcrossing, but this must be done carefully to avoid losing the diversity you worked to gain.
Let’s look at what happens genetically with each backcross:
As you can see, each backcross reduces the genetic contribution of breed B by half. If you do serial backcrosses, you will eventually lose most of the new diversity, putting the population right back where it started.
Instead, to retain diversity while restoring breed type, use a structured breeding plan that:
✔ Uses multiple unrelated outcross dogs
✔ Balances careful selection with genetic management tools like DNA testing
✔ Prioritizes diversity early on, before selecting too heavily for traits
This is where expert guidance and genetic testing tools can make a critical difference in the long-term success of a crossbreeding program.
Crossbreeding is a Tool, Not a Threat
At some point, every purebred breed will need to take steps to manage inbreeding and restore lost genetic diversity through cross breeding. This is because animal populations in closed gene pools become more and more inbred over time and eventually go extinct due to inbreeding depression that reduces fertility and lifespan and a high burden of health problem.
As shown above, returning to breed type can be fast and easy, taking as few as three generaetions. But the real challenge is restoring type while keeping genetic diversity intact. Livestock breeders have been successfully using structured crossbreeding strategies for decades, often without access to the molecular tools now available to dog breeders.
For those concerned about potential changes to the breed and its gene pool from crossbreeding, note that the gene pool of your breed is not static now. It changs as a result of inbreeding because:
Crossbreeding does not threaten breed preservation. In fact, crossbreeding is one of the most powerful tools available to protect a breed’s genetic health and long-term viability. Skilled breeders should use crossbreeding strategically with other breeding strategies like outcrossing and inbreeding to maintain breed quality while ensuring genetic health.
Crossbreeding, when done correctly, should be viewed not as a last resort, but as a valuable strategy for breed preservation and health.
Your focus in a crossbreeding program should be on genetic diversity, not specific traits.
Why? Because trait selection requires genetic diversity. You can’t select for particular traits if the necessary alleles aren’t present. By introducing new diversity, you are building the genetic foundation needed to re-establish breed traits later.
Also, keep in mind that genetic health is more than just managing disease mutations. Many traits, including immune system function and adaptability, rely on complex genetic interactions. Focusing too soon on specific physical traits can limit genetic progress and reduce the overall health benefits of crossbreeding.
Remember that for polygenic traits, F1 puppies will get a random collection of only half the alleles of the parent used in the cross. It’s unlikely that a puppy will inherit all of the variants involved in a complex trait. Again, focus on capturing maximum genetic diversity, then you can use focused selective breeding to shape traits with the most diverse genetic pantry possible.
4) What about genetic disorders?
Every animal carries recessive mutations, but these typically do not cause disease as long as the locus remains heterozygous (i.e., one normal allele is present). Recessive mutations become a problem as a result of inbreeding, which produces homozygosity. The key to good physical health is low inbreeding is supported by high genetic diversity.
Trying to reduce genetic health disorders by eliminating recessive mutations from the gene pool is difficult (you need to find every last recessive mutation) as well as genetically destructive, because selection against mutations will work against your goal of protecting genetic diversity.
A more effective approach is to:
✔ Focus on maximizing genetic diversity and avoiding inbreeding to reduce the risk of harmful mutations becoming homozygous
✔ Recognize that many disorders are complex or polygenic, meaning we don’t always know which genes are involved
✔ Avoid extreme selection pressure that could narrow the gene pool further
The safest way to minimize risk from inherited disorders is to restore a healthy genetic foundation first.
5) How should backcrossing be handled?
Restoring breed type after a crossbreed introduction often involves backcrossing, but this must be done carefully to avoid losing the diversity you worked to gain.
Let’s look at what happens genetically with each backcross:
- First-generation (F1) cross: 50% breed A / 50% breed B
- First backcross (A x F1): 75% A / 25% B
- Second backcross (A x 75/25): 87% A / 13% B
- Third backcross (A x 87/13): 93% A / 7% B
As you can see, each backcross reduces the genetic contribution of breed B by half. If you do serial backcrosses, you will eventually lose most of the new diversity, putting the population right back where it started.
Instead, to retain diversity while restoring breed type, use a structured breeding plan that:
✔ Uses multiple unrelated outcross dogs
✔ Balances careful selection with genetic management tools like DNA testing
✔ Prioritizes diversity early on, before selecting too heavily for traits
This is where expert guidance and genetic testing tools can make a critical difference in the long-term success of a crossbreeding program.
Crossbreeding is a Tool, Not a Threat
At some point, every purebred breed will need to take steps to manage inbreeding and restore lost genetic diversity through cross breeding. This is because animal populations in closed gene pools become more and more inbred over time and eventually go extinct due to inbreeding depression that reduces fertility and lifespan and a high burden of health problem.
As shown above, returning to breed type can be fast and easy, taking as few as three generaetions. But the real challenge is restoring type while keeping genetic diversity intact. Livestock breeders have been successfully using structured crossbreeding strategies for decades, often without access to the molecular tools now available to dog breeders.
For those concerned about potential changes to the breed and its gene pool from crossbreeding, note that the gene pool of your breed is not static now. It changs as a result of inbreeding because:
- Every generation of inbreeding increases homozygosity, changing the composition of the gene pool
- Every generation, alleles are lost through genetic drift, also changing the composition of the gene pool
Crossbreeding does not threaten breed preservation. In fact, crossbreeding is one of the most powerful tools available to protect a breed’s genetic health and long-term viability. Skilled breeders should use crossbreeding strategically with other breeding strategies like outcrossing and inbreeding to maintain breed quality while ensuring genetic health.
Crossbreeding, when done correctly, should be viewed not as a last resort, but as a valuable strategy for breed preservation and health.
|
To learn more about the genetics of dogs, check out
ICB's online courses
***************************************
Visit our Facebook Groups
ICB Institute of Canine Biology
...the latest canine news and research
ICB Breeding for the Future
...the science of animal breeding
***************************************
ICB's online courses
***************************************
Visit our Facebook Groups
ICB Institute of Canine Biology
...the latest canine news and research
ICB Breeding for the Future
...the science of animal breeding
***************************************
