By Carol Beuchat PhD
I asked the members of my ICB Breeding for the Future Facebook group to rate their understanding of genetic management and that of the people in their breed.
Like the folks that live in the mythical town of Lake Wobegon, where everyone is “above average”, most people responded to the "Rate Yourself" post with a score of 3 or more on a scale of 1 to 5. And pretty much everybody said that the overall level of understanding of the people in their breed was low (lots of 1s for this).
The latter response is very worrisome. Here’s why.
Find your breed on this graph, which is the genomic (from DNA) inbreeding of a large number of purebred dog breeds. These data are consistent with data from several other studies of different populations, so we can assume that this is a fair representation of inbreeding in these breeds.
The green line is inbreeding of 6.25% (mating of first cousins), yellow is 12.5% (mating of half sibs), and red is 25% (full-sib mating). (I made this graph to highlight the data for Cavaliers for another post; the black line at about 41% is the average inbreeding of this breed.)
Like the folks that live in the mythical town of Lake Wobegon, where everyone is “above average”, most people responded to the "Rate Yourself" post with a score of 3 or more on a scale of 1 to 5. And pretty much everybody said that the overall level of understanding of the people in their breed was low (lots of 1s for this).
The latter response is very worrisome. Here’s why.
Find your breed on this graph, which is the genomic (from DNA) inbreeding of a large number of purebred dog breeds. These data are consistent with data from several other studies of different populations, so we can assume that this is a fair representation of inbreeding in these breeds.
The green line is inbreeding of 6.25% (mating of first cousins), yellow is 12.5% (mating of half sibs), and red is 25% (full-sib mating). (I made this graph to highlight the data for Cavaliers for another post; the black line at about 41% is the average inbreeding of this breed.)
If your breed’s average inbreeding is 25%, that means that, on average, the parents of a litter are as genetically similar as full siblings, even if they appear to be relatively unrelated on pedigrees. Most breeders would not breed littermates together. Yet, in many breeds, the typical sire and dam are more closely related than this.
Inbreeding in dogs is FAR higher than in any other mammal, wild or domestic. Inbreeding of wild animal populations is usually in the very low single digits. Breeders of livestock begin to panic as inbreeding approaches 10% because the negative effects are so significant. In fact, they worry about every percentage point of increase; on this chart, the livestock people are wringing hands because "in all three breeds the inbreeding coefficients are the highest they have ever been," and they haven't even cracked 10% yet.
Inbreeding in dogs is FAR higher than in any other mammal, wild or domestic. Inbreeding of wild animal populations is usually in the very low single digits. Breeders of livestock begin to panic as inbreeding approaches 10% because the negative effects are so significant. In fact, they worry about every percentage point of increase; on this chart, the livestock people are wringing hands because "in all three breeds the inbreeding coefficients are the highest they have ever been," and they haven't even cracked 10% yet.
Think about this. You cannot "breed for health" when levels of inbreeding are higher than about 5%, because above this the negative consequences and risk of genetic disorders increases linearly with inbreeding. In a closed gene pool, inbreeding can ONLY increase over generations, and the gene pool can ONLY get smaller. So, despite the best efforts of breeders to improve health, the quality of the gene pool deteriorates inexorably over time, as alleles that were in the gene pool 50 years ago, or 10 years ago, or even in the last generation, are lost to the breed.
This means that, because of the facts of basic genetics, you cannot “preserve” a breed in a closed gene pool. You might breed in a way that attempts to limit the damage to the gene pool, but you cannot preserve a breed if alleles necessary for function and health are lost from the gene pool every generation. You can be a “responsible” breeder," and make choices that attempt to limit the damage, but you cannot be a ”preservation” breeder, not when more genes necessary for the body to function are being lost every generation.
Can we at least say that we are breeding responsibly, i.e., making breeding decisions that will limit the damage to a breed’s gene pool? Let’s look at some data.
These graphs are from Lewis et al (2015) and are based on the pedigree records of the UK Kennel Club. Note that the data were not digitized before 1980, so the graphs start there, and the COIs are much lower than actual values because the ancestors from 1980 back to founders are not included in the calculation. Also, ban on importing dogs into the UK was lifted in 2000, and the incomplete pedigree data for those dogs make it look like the average population inbreeding is going down after that, which is probably not the case.
The blue line is the average COI computed from the pedigree data. The red line is the level of inbreeding that would be expected if the dogs in the population were breeding randomly. If breeders were making a strong effort to avoid inbreeding, the blue line would be below the red line; if breeders are preferentially breeding dogs that are more closely related than average, the blue line would be above the red line.
These graphs tell us about the overall breeding strategies being used in each breed. Breeders are preferentially inbreeding. (I have grabbed a few of the breeds that have a population large enough to show a trend instead of a line that goes all over the place.)
Can we at least say that we are breeding responsibly, i.e., making breeding decisions that will limit the damage to a breed’s gene pool? Let’s look at some data.
These graphs are from Lewis et al (2015) and are based on the pedigree records of the UK Kennel Club. Note that the data were not digitized before 1980, so the graphs start there, and the COIs are much lower than actual values because the ancestors from 1980 back to founders are not included in the calculation. Also, ban on importing dogs into the UK was lifted in 2000, and the incomplete pedigree data for those dogs make it look like the average population inbreeding is going down after that, which is probably not the case.
The blue line is the average COI computed from the pedigree data. The red line is the level of inbreeding that would be expected if the dogs in the population were breeding randomly. If breeders were making a strong effort to avoid inbreeding, the blue line would be below the red line; if breeders are preferentially breeding dogs that are more closely related than average, the blue line would be above the red line.
These graphs tell us about the overall breeding strategies being used in each breed. Breeders are preferentially inbreeding. (I have grabbed a few of the breeds that have a population large enough to show a trend instead of a line that goes all over the place.)
The name of each breed is on the gray bar at the top.
(Graphs from Lewis et al 2015, Additional Files)
(Graphs from Lewis et al 2015, Additional Files)
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We want to preserve breeds. We want to produce healthy, long-lived dogs. But look at the data. How are we going to do this?
In response to the ban on breeding Cavaliers and Bulldogs in Norway, the clubs have responded that the breeders are in the best position to solve the problems and are working hard to do this. But inbreeding will continue because it is unavoidable in a closed gene pool. DNA testing can prevent disorders caused by a single, recessive mutation for which we have a test, but we do nothing to control the many other recessive mutations we know are lurking in the gene pool, and selection is doing a poor job of managing the problems that are likely polygenic. Plus, we are preferentially inbreeding, increasing the risk of producing genetic disorders from mutations we don't yet know about.
I noted up at the top that, in a survey of the people in my Facebook group, ICB Breeding for the Future, most people rated their understanding of the principles of genetic management and breeding for health at a 3 or higher on a scale of 1-5, where 5 is highest. They also overwhelmingly rated the average understanding of the people in their breed at 1.
If we want to have purebred dogs, we need to solve some serious problems, we need to get it right the first time, and we need to do it soon. The kennel clubs say “We can do this,” but breeders assess the general level of genetic management expertise of their colleagues as rock bottom.
I can probably count on one hand the number of dog breeders I know that have enough expertise in population genetics to “know what they don’t know,” and all of those people are professional scientists that happen to also breed dogs. Beyond that, there is an army of “Facebook experts” - people that might know something about little bits of a topic but dispense advice as if expert. Invariably, they say things that are incorrect, because they don’t know enough to appreciate the nuances, complications, and depth of concepts. They don’t know what they don’t know, and most people don't know the difference. These experts don’t do any topical coursework (e.g., I don't see them in ICBs online courses for breeders), and they usually have no background in science at all. What they “know” has mostly come from things they read on Facebook written by other people with no expertise.
If you are tackling a very difficult problem, and if getting it wrong could result in catastrophe, these Facebook experts are extremely dangerous. Most breeders in my survey judged the expertise in their own breed as very poor. Most probably wouldn’t know good advice from bad; they are likely to be most swayed by things that sound “logical” or “make sense”. But their perspective is on managing the genetics of individual dogs. The genetics of populations are quite different, and indeed “the right thing to do” can often be counter-intuitive. You’ve heard that you should only “breed the best to the best”, but this will actually make it harder to improve traits and will ultimately lead to extinction of the population. In fact, this is why we are in this difficult spot, and continuing to use this breeding strategy is the hammer that will sink the last of the nails into the coffin. This is not an opinion; this is a necessary consequence of the mathematics behind population genetics. If you don't know this, then the "best to the best" advice seems like a good thing to do. But it's not.
The Norwegian kennel and breed clubs argue that they can fix the health problem of Cavaliers and Bulldogs by continuing to do the things they think will work. They haven’t worked so far, and they won’t. But apparently they don’t know that.
The Norwegian court offered that crossbreeding to solve the health issues would be allowed, but the feedback on Facebook has been adamantly opposed to even considering cross breeding programs. So, if the Norwegians have a plan to fix this without crossbreeding, I would like to hear how they will do it.
The breeds in the spotlight in Norway have to come up with a plan to address the issues that put them in violation of the Norwegian Animal Welfare Act. The Norwegians are on the hot seat right now, but every breed has an inbreeding problem that is incompatible with sustainable breeding, incompatible with “preservation” breeding, and incompatible with health. What breeds have a plan to address their growing list of genetic health issues, which will only continue to grow? How will they know if their plan will work? What will they do if it doesn’t?
In response to the ban on breeding Cavaliers and Bulldogs in Norway, the clubs have responded that the breeders are in the best position to solve the problems and are working hard to do this. But inbreeding will continue because it is unavoidable in a closed gene pool. DNA testing can prevent disorders caused by a single, recessive mutation for which we have a test, but we do nothing to control the many other recessive mutations we know are lurking in the gene pool, and selection is doing a poor job of managing the problems that are likely polygenic. Plus, we are preferentially inbreeding, increasing the risk of producing genetic disorders from mutations we don't yet know about.
I noted up at the top that, in a survey of the people in my Facebook group, ICB Breeding for the Future, most people rated their understanding of the principles of genetic management and breeding for health at a 3 or higher on a scale of 1-5, where 5 is highest. They also overwhelmingly rated the average understanding of the people in their breed at 1.
If we want to have purebred dogs, we need to solve some serious problems, we need to get it right the first time, and we need to do it soon. The kennel clubs say “We can do this,” but breeders assess the general level of genetic management expertise of their colleagues as rock bottom.
I can probably count on one hand the number of dog breeders I know that have enough expertise in population genetics to “know what they don’t know,” and all of those people are professional scientists that happen to also breed dogs. Beyond that, there is an army of “Facebook experts” - people that might know something about little bits of a topic but dispense advice as if expert. Invariably, they say things that are incorrect, because they don’t know enough to appreciate the nuances, complications, and depth of concepts. They don’t know what they don’t know, and most people don't know the difference. These experts don’t do any topical coursework (e.g., I don't see them in ICBs online courses for breeders), and they usually have no background in science at all. What they “know” has mostly come from things they read on Facebook written by other people with no expertise.
If you are tackling a very difficult problem, and if getting it wrong could result in catastrophe, these Facebook experts are extremely dangerous. Most breeders in my survey judged the expertise in their own breed as very poor. Most probably wouldn’t know good advice from bad; they are likely to be most swayed by things that sound “logical” or “make sense”. But their perspective is on managing the genetics of individual dogs. The genetics of populations are quite different, and indeed “the right thing to do” can often be counter-intuitive. You’ve heard that you should only “breed the best to the best”, but this will actually make it harder to improve traits and will ultimately lead to extinction of the population. In fact, this is why we are in this difficult spot, and continuing to use this breeding strategy is the hammer that will sink the last of the nails into the coffin. This is not an opinion; this is a necessary consequence of the mathematics behind population genetics. If you don't know this, then the "best to the best" advice seems like a good thing to do. But it's not.
The Norwegian kennel and breed clubs argue that they can fix the health problem of Cavaliers and Bulldogs by continuing to do the things they think will work. They haven’t worked so far, and they won’t. But apparently they don’t know that.
The Norwegian court offered that crossbreeding to solve the health issues would be allowed, but the feedback on Facebook has been adamantly opposed to even considering cross breeding programs. So, if the Norwegians have a plan to fix this without crossbreeding, I would like to hear how they will do it.
The breeds in the spotlight in Norway have to come up with a plan to address the issues that put them in violation of the Norwegian Animal Welfare Act. The Norwegians are on the hot seat right now, but every breed has an inbreeding problem that is incompatible with sustainable breeding, incompatible with “preservation” breeding, and incompatible with health. What breeds have a plan to address their growing list of genetic health issues, which will only continue to grow? How will they know if their plan will work? What will they do if it doesn’t?
Purebred dog lovers face two huge challenges. First, we must fix the significant inbreeding problem that imperils essentially every breed.
Then, once we have inbreeding down to a reasonable level, we need to breed sustainably, which means we have to control inbreeding and loss of genetic diversity. To do this, breeders will need to understand population genetics, which provides the tools used for the genetic management of animal populations.
Are you thinking you already know a lot about population genetics? Among the essential topics you should be able to explain and discuss are these, for example: linkage disequilibrium, founder genome equivalents, effective population size, the Hardy-Weinberg equation, heritability, fitness, mean average kinship, observed and expected heterozygosity, and genetic drift.
Then, once we have inbreeding down to a reasonable level, we need to breed sustainably, which means we have to control inbreeding and loss of genetic diversity. To do this, breeders will need to understand population genetics, which provides the tools used for the genetic management of animal populations.
Are you thinking you already know a lot about population genetics? Among the essential topics you should be able to explain and discuss are these, for example: linkage disequilibrium, founder genome equivalents, effective population size, the Hardy-Weinberg equation, heritability, fitness, mean average kinship, observed and expected heterozygosity, and genetic drift.
If these terms don't trip off your tongue, if you you are not confident that you could easily explain them, then you won't be able to follow the discussion and rationale of the breeding plans your breed will need to follow. To be fair, these are not terms the average dog breeder would ever run into in general discussions about breeding. People don't usually sit around the ring discussing the effective number of founders of their breed. Even if you have a degree in biology, most of these terms would be unfamiliar. So these will probably be unfamiliar to you and your fellow breeders. But if you want to be part of implementing a breeding program to improve the health of your breed, the sooner you work on building a sound understanding of population genetics, the better.
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There aren't many ways for breeders to learn population genetics, which is mostly advanced topics based on mathematics. When I was unable to point breeders towards a resource for learning about population genetics at a basic but useful level, I created some online courses specifically for dog breeders with no background in science. While I realize this looks self-serving, it really is the only option available to dog breeders without a degree in biology. Find the time to invest in education; the payoff will be immediate and continue for as long as you breed. Be an education advocate within your breed; you and your fellow breeders all must share a single gene pool, and breeders won't support a breeding strategy they don't understand.
The next ICB course for dog breeders about genetic management is "Strategies for Preservation Breeding," which starts 1 July 2022. Register now! |
REFERENCES
Bannasch E et al 2021. The effect of inbreeding, body size and morphology on health in dog breeds. Canine Medicine and Genetics 8:12. doi.org/10.1186/s40575-021-00111-4
Lewis et al 2015. Trends in genetic diversity for all Kennel Club registered pedigree dog breeds. Canine Genetics & Epidemiology 2:13. DOI:10.1186/s40575-015-0027-4
Bannasch E et al 2021. The effect of inbreeding, body size and morphology on health in dog breeds. Canine Medicine and Genetics 8:12. doi.org/10.1186/s40575-021-00111-4
Lewis et al 2015. Trends in genetic diversity for all Kennel Club registered pedigree dog breeds. Canine Genetics & Epidemiology 2:13. DOI:10.1186/s40575-015-0027-4
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