By Carol Beuchat PhD

In all animals, traits are altered from one generation to the next by natural or artificial selection. Genes for beneficial traits are preferentially passed on to offspring, while genes for detrimental traits are not. Over many generations, these gradual changes in gene frequency can add up to produce dramatic changes in size, shape, and behavior, and there is no better example of this than in dogs. 

Although some of the goals have changed with the times, selection for behavioral traits is still at the core of most breeding programs. But anybody who has tried it can tell you that producing dogs that will display the behaviors you want isn't easy. A highly motivated working dog can produce a slacker, and a sweet tempered companion dog can produce one that is snappy and ill-tempered. Careful selection does not always produce what the breeder expects. The reason, of course, is that most behavior is complex and reflects not only the expression of many genes but also the influence of environmental factors. Understanding the dual contributions of genetics and environment to behavior is the crux of the debate about "nature vs nurture".

In fact, most behavior is a product of both nature and nurture; both genes and environment affect behavior. Efficient selection for desired behavior requires an understanding of the relative roles of genes and environment. The tool we can use to do this is a concept called "heritability".

​There is much misunderstanding about the meaning of heritability and, although heritability plays a key role in selection programs in other domestic animals, it has not been widely used by the dog fancy. This is unfortunate, because a breeder that understands heritability can substantially improve the efficiency of selection in their breeding program, not just for behavior but for any trait that is affected by both genetics and environment (e.g, hip dysplasia, obesity).

So, what is heritability?

The word itself suggests that it has something to do with genetics, and indeed it does, but probably not in the way you think.

​Here is a formal definition of heritability:

Heritability is the fraction of the variation in phenotype of a trait that is accounted for by the variation in genotype.

Phenotype is simply the expression of a trait, whether it be behavior, anatomy, function, or whatever. Genotype is the genetic makeup of the animal. So for example, if we are talking about the heritability of aggression in dogs, we are addressing how much of the variation in aggression from dog to dog can be attributed to variations among them in genotype.

To assess heritability, we need to document the variation in phenotype in a group of animals. Therefore, heritability is a property of a population, not of a trait. 

This is where most people get tripped up by the meaning of heritability. Let's try to clarify by looking at some of the common misunderstandings about heritability.

Heritability Misconceptions

Misconception 1. "A heritability of 0.25 means that 25% of a trait is determined by genetics".

I'm sure you have heard this one. Look back at the definition of heritability that we stated above:

​"Heritability is the fraction of the variation in phenotype of a trait that is accounted for by variation in genotype.

Heritability is about the variation in a trait from animal to animal, not the expression of the trait itself. If the heritability of a trait is 0.25 (or we can say 25%), that means that 25% of the variation in the trait in a group of animals can be attributed to variation in their genes. By extension, we can also say that 75% of the variation in our group of animals is the result of variation in environment - factors other than genetics.

Misconception 2. "A low heritability means that traits are not determined by genes."
​
Again, go back to our definition of heritability. A low heritability means that only a small amount of the variation in a trait in a group of individuals is a result of variation in their genes. If heritability is greater than 0, then genes do have some effect on the expression of the trait. It might be small, but at least some of the variation is due to genes.

But here's something tricky: a heritability of zero could either be because a trait is not affected by genes at all (e.g., the color of the shirt you're wearing today), or there is no variation in the trait and therefore none in the genes involved. For instance, the vast majority of people have five fingers on each hand. Having five fingers is definitely genetic, but the heritability of "number of fingers" is zero because there is no variation in either the trait or in the genes for the trait. And of course, you don't have a gene for "red shirt on Tuesday", although your choice might reflect the fact that red is especially attractive to you when you're stressed (genes), and you happened to have a red shirt (environment).

Likewise, if there are no environmental effects on the expression of a trait that varies among individuals, then the heritability will be equal to one: all of the variation in the phenotype of the trait can be accounted for by variations in the genes in each individual.

Misconception 3. "Heritability is a fixed value for a particular trait".

For the reason why this is not true, look again at the definition. Heritability refers to the fraction of phenotypic variation that can be attributed to genes vs environment. For example, body weight is influenced by genes that affect size, but it is also affected by food consumption and amount of exercise. The offspring of small dogs will tend to be small because of genetics, but dogs that are fed more and get less exercise will probably weigh more than ones that don't. The phenotype (body weight) will vary from individual to individual, and some portion of that variation will be a consequence of genes and the remainder will be due to environment. Consequently, the heritability of body weight in one group of dogs can be very high (if the environment and food are the same for all the dogs) or it can be low (if dogs eat as much as they want and have both a large play area and sofa). 

This is a key point: Heritability is not a fixed number for a trait. It reflects the relative contribution of genetics to the variation in a trait. If the variation in the trait is high because of variation in environmental factors, then the heritability in that population at that time will be low. 

You're probably still a bit confused about this heritability thing. It's definitely tricky, and I have a few examples of genetics textbooks that get it wrong! But have a look at these two videos, which I think do a good job of explaining heritability in the context of behavior using a few simple examples. Afterwards, I'll tell you about "the kicker" - the thing that makes heritability so important for breeders to understand.

"The Kicker"
​
​How important is it for breeders to understand all this nonsense about heritability? Very, and I'll tell you why.

Improving (or removing) a trait involves selecting those individuals that have the genes for the trait you want (or don't). Since we usually have no idea what the genes are that are involved in complex traits, we make selections based on phenotype - the expression of that trait. We assume that dogs that have the trait we want also have the genes we want and will pass them to their offspring. But is this assumption true? Maybe not.

If the heritability of a trait is high, then phenotype will be a good reflection of genotype. The variation in the trait in a group of animals will reflect the variation in the genes they inherited for a trait. Choosing dogs with the best phenotype will also be choosing the dogs with the best genotype.

But if heritability of a trait in a population is low, then the phenotype of the trait will not be a good reflection of genotype. A dog with high levels of aggression might have the genes for low aggression, but poor socialization or some bad experiences early in life have had a large, negative effect on the expression of that trait. That is, a dog with good genes can display a bad phenotype.

But you are only using phenotype to select the best breeding candidates; you don't know what genes they have. You are counting on your ability to pick the dogs with the genes you want based on your assessment of phenotype. If variation in phenotype doesn't accurately reflect differences in genotype, you won't be very good at identifying the best dogs to use (or not) in your breeding program. 

Now think about this. You are selecting for temperament. You don't breed animals with bad temperaments. But the heritability of most aspects of temperament is relatively low, because differences among dogs can reflect a variety of environmental factors you have no control over or even know anything about. You could be removing dogs from the gene pool that have the genes for good temperament but had bad experiences as a puppy.

If you're a dog breeder, this is clearly a problem. If heritability is low, phenotype is not telling you what you need to know about genotype. What can you do about this?

The simplest thing to do is evaluate additional animals that have similar genotypes, such as parents, siblings, and offspring. If related dogs don't have the temperament you want, it is unlikely that they have the genes you want either. Similarly, if good temperaments are common among related dogs, then a dog is likely to have good genes even though the expression of the trait in that dog isn't as good as you would like.

This isn't an argument to breed dogs with bad temperaments. Rather, it's a reason to try to get the best possible assessment of the genotype of a dog by considering the phenotypes of closely related dogs as well. This is one of those "baby-and-bathwater" things. Don't toss out the important thing (the genes) because of dirty bathwater. (Perhaps you have heard of "estimated breeding values" (EBVs). This is a statistical way to get a better assessment of the genotype of a dog by including information about the trait in related dogs.)

You can see that if you want to improve traits through selective breeding, it's important for you to know the heritability of the traits you are trying to select for (or against). If heritability is high, you will do a better job of choosing the dogs with the genes you want based on their phenotype. If heritability is low, phenotype will less accurately reflect genotype, and it will be harder to determine which dogs have the genes you want.

You can improve the efficiency of selection in your breeding program by doing things that will increase heritability of the traits of interest. For example, you can assess the trait under conditions that are as similar as possible for all the candidate dogs. This will reduce the amount of variation in the trait that is due to differences in environment, and higher heritability means that phenotype will be a better predictor of genotype. Evaluate an entire litter at the same time in the same place. Test all of the candidate bomb-sniffing dogs under carefully controlled conditions. Assess herding behavior of working dogs using the same herd and under conditions that are as similar as possible. By reducing environmental effects, what you see will more accurately reflect genotype.

Think about the traits you select for in your breeding program, learn about their heritabilities, and use this information to improve the efficiency of your breeding program.

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To understand the rest of this, you need to read the blog I posted yesterday, so if you missed it you need to click on the link and read it now. I'll wait here for you. 

Are we watching the extinction of a breed?

Quite a downer, wasn't it? When I posted it I expected to receive a fusillade of abuse from "responsible" breeders. But I didn't. I got these, from people in Dobermans as well as other breeds:

This is an article that every breeder should read. I no longer believe <X> breed can be saved. I no longer even want it to, at least in the manner in which breeders have been going. I don't believe this new test will matter in the long run, and by long run I don't mean 50 years, but 20 years from now. I cannot any longer feel as if the dogs can wait for that better future where <this disease> does not torment them. This breed is broken. All we can do is keep it propped up. No dog should be created to live this way. Although this article focuses on Dobermans, the X is also in trouble and the points made in this article need to be taken in and deeply considered as they pertain to all pure breed dogs. Thank you Carol Beuchat for speaking out plainly.

To be fair, I will confess that there were a few folks that had something negative to say. I just have to share with you this gem offered by Robyn Dubbert:

I want to share one more thing with you that was posted as a comment by Ruth Stolzewski in the ICB Breeding for the Future group.

"The Doberman doesn't die of inbreeding. It dies of human ignorance. This is the video I made for Doberman lovers in Germany 3 years ago: https://youtu.be/mL4wuv26068. And still the German Doberman club neglects the existence of the disease and does NOTHING to preserve it. And he does this under the roof of the German Kennel Club which calls itself the club with the strictest rules. Well what are rules worth if they are not enforced? The whole dog breeding world is just a false system in which human greed and ego comes first and the dog's well being comes last. That's the sad reality. And it does not change."

Go get a cup of tea and watch her moving video about the tragedy of DCM in Dobermans.

The familier themes are all there. Researchers studying the disorder. Geneticists searching for the gene. Acceptance by breeders that it's an unfortunate disorder in the breed, and even denial by the Kennel Club that there is any problem at all. You can be sure that for every death there are many hearts broken. In many cases the death of the dog left a loving owner with the mental image of a dog collapsing that they will never be able to "unsee".

Registrations of most purebred breeds have been dropping, but the decline in Dobermans is breathtaking. This graph is from the report compiled by the UK Kennel club and published on their website (you can download a copy below). After a burst of popularity in the 1980s, registrations crashed then seemed to settle down to about 3,000 per year. In the last 10 years, however, registrations have dropped like a rock. 

So, what now? If breeders are going to try to fix the health problems and save this breed, they better get started on it soon or there will be nothing left to save. They don't have time to bicker about whose fault it is, or which lines are worst and which might still be healthy. They need to make a plan, it needs to be global, and it needs to be sound.

​This is not a problem breeders or clubs will be able to solve themselves. This will be comparable to the rescue of a wildlife species in imminent danger of extinction. These kinds of rescues are very challenging under any circumstances, but rescue of the Doberman will take this to another level of difficulty. Real animal populations get sucked into the "extinction vortex" as inbreeding increases above about 10% because of low fertility, poor health, and short lifespans. Endangered species don't usually hang on until the level of inbreeding is 40% or 50% and a good fraction of the population is dropping dead before they are old enough to breed.

Breeders will need some serious expertise to help them fix this. It's going to take a lot of time, a lot of effort, and a lot of money to turn this boat around. Don't waste time worrying about what should be done and how to do it. Call in the doctor and get busy building a long-term plan. The longer you wait to get started, the harder it will be, because inbreeding will continue to increase and more and more of the gene pool will be lost. And, of course, more Doberman owners will experience the anguish of losing a beloved member of the family to a known genetic disorder.

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​

By Carol Beuchat PhD

When I sat down at my desk this morning ready to tackle the tasks of the day, I did my usual quick scroll through my Facebook timeline. Right away, I ran into this video of a game of fetch with a Doberman. You need to watch this to the end.

​Then just a few posts down there was this.

I don't know these dogs and I don't know these people, but my heart breaks for them. I've set aside what I planned to do today to tell you what I think about this.

The dogs we love are dying. Biologists can tell you why this is happening, and in fact even animal breeders 100 years ago could have told you why this is happening. I've written dozens of blog posts on the ICB website explaining why this is happening.

Inbreeding affects health. At low levels of inbreeding, say 5% to 10%, there are effects on fertility, litter size, puppy mortality, and "vigor". There are also increases in the number of genetic disorders. The higher the level of inbreeding, the more negative the effects.

This is not folklore. This is fundamental, basic genetics. Inbreeding increases the expression of genetic disorders and has a negative effect on health in general. These are facts. If somebody is trying to convince you otherwise, you need to find a different mentor.

Inbreeding is necessary to fix type and improve consistency in domestic animals. This is how the breeds were created. These benefits can be appreciated at levels of inbreeding less than 10%.

Among purebred, recognized dog breeds, type was fixed long ago. The Dobermans above might not win in the ring, but they are recognizably Dobermans.

Here is the elephant in the room. Our dogs are dying of inbreeding. Decades of inbreeding in a quest for the ever more perfect dog has resulted in the loss of genes that are essential to life. However perfect and beautiful the dogs might be on the outside, on the inside they are broken.

What are we doing about this? We seem to be doing a lot. There are research studies, DNA tests, health seminars, disorder-specific Facebook groups, and so on.

But our dogs are dying of inbreeding. None of the things we are doing will cure inbreeding. Scientists can't cure inbreeding. Inbreeding must be cured by breeders.

I founded ICB four years ago because there was an increasing number of research papers being published about the negative effects of inbreeding on the health of dogs, but breeders didn't seem to be getting the message. There was really no place for breeders to go to get factual information, and they didn't have access to the resources and expertise they would need to address the growing problem. So ICB was born.

Four years on, thousands of students have taken ICB courses, but still it's just a trivial fraction of the number of breeders. A surprising number of ICB students are not breeders themselves, but are considering breeding in the future or are concerned about the growing health crisis in purebred dogs. For the most part, the "mainstream" breeders are not in these courses.

Perhaps this is why we seem to have settled into a standard approach in dealing with genetic disorders in dogs.

​To the breeders, celebrity psychologist Dr Phil would ask "And how's this been workin' for ya'?"

The honest answer is that it's not. 

What's the problem here? Breeders are looking to science for solutions to health problems, and the scientists study genetics and disease.

But the dogs are dying of inbreeding, and that is the problem we need to fix. We are focused on consequence when the solution lies in the cause. We are continuing to enjoy our cigarettes while we toss money at lung cancer research and assume that with hope, prayer, and patience things will get better. We are learning a lot about the problems that are caused by inbreeding, but we are not solving the problem.

Facebook posts like the ones at the beginning haunt me. The daily obituaries of dogs that died before their time clash with the proud announcements on Facebook about a young dog taking a five point major in stiff competition, or a dog achieving Grand Champion status, or a breeder-handler winning the group. Even more grating are the pronouncements about "responsible breeders" and more recently "preservation breeders". Dobermans are dropping dead of heart failure and have been for decades, while breeding continues. 

Look into the future. What scenario do you envision for how this will end?

​Science can help you with this. Doberman lover and scientist Dr Sonia Garcia Herdez put the information together to do a projection. Using published information about the frequency of DCM (dilated cardiomyopathy) in Dobermans, she created this nice graph of the known and projected frequency of the disease.

The graph shows that if we extrapolate from the past incidence rates into the future, by 2020 (that's four years from now!), 72% of European Dobermans will be afflicted with DCM. She provides the equation for the line, so I am able to do a bit of math and tell you that in 2039, essentially 100% of European Dobermans will have DCM. Anybody that breeds or loves Dobermans and is not already well into their sixties should be able to witness the sad extinction of this breed.

Can't we make this better through selective breeding? We don't seem to be making much progress so far, and the available genetic data paint a grim picture. Below is a graph based on DNA genotyping of Dobermans done by the Finnish company MyDogDNA (MDD). (I have compiled these graphs for all breeds for convenience here.)

​The graph is a frequency distribution of "heterozygosity". Heterozygosity is the fraction of loci in a dog's genome that have two different alleles. Inbreeding decreases heterozygosity; that is, inbreeding increases homozygosity, meaning both alleles are the same because an animal inherited the same allele from both parents. On the graph, the dogs with the lowest inbreeding are to the right and those with the highest inbreeding are to the left, indicated by the color scale from green to red under the graph. The orange line on this graph is for "all dogs" in their database and the green line is for a selection of similar breeds (pinschers, schnauzers, etc).

The blue line is for Dobermans and includes dogs from the US, UK, Finland, Russia, Australia, and Ukraine. The median level of heterozygosity reported by MDD for Dobermans is 27% (that should be close to the peak in the blue line). This is quite a bit lower than the median for all dogs, and it's even worse than the comparison population. 

​But is this really all that bad? Have a look at the graph below.

I have compiled the data for median heterozygosity of most of the breeds in the MDD database, and they are ranked here from worst (left) to best (right). The Doberman is indicated by the red arrow, well down in the rankings. (You can download a larger version of this graph below.)

Yes, this is bad. These data show that genetic diversity in Dobermans is extremely low. You can't improve a trait if there is no genetic variation in the population to select from. Genetic diversity in Dobermans is low and probably half the breed is afflicted with DCM. For Doberman lovers, I think there is much heartbreak in the future.

I've talked to a fair number of Doberman breeders about this. I even went to the Doberman National Specialty a few years ago to talk to more breeders. I found that most Doberman breeders love their breed with a passion, and for many people Dobermans are their life. I am convinced that breeders will continue to battle diligently against DCM until the last dog dies. But there is no solution to this problem in what we are already doing.

Above, I've presented you with the data. Here is where I am going to offer my opinion.

DNA testing does not make somebody a "responsible" breeder. Caring for the heritage of your breed does not make you a "preservation" breeder. Pride and love and dedication are all terrific, but they will not prevent the heartbreak that awaits thousands of Doberman owners in the future. Breeders need to DO something about this. Breeders need to step up to the plate and acknowledge that continuing to breed dogs that are likely to die of a genetic disorder is irresponsible, unethical, and inhumane. That is certainly how the average, everyday dog lover feels. This is also how I feel.

The Doberman was not created in its present form by a dog-loving God. It is a "blender" breed, created by a man who mixed a bit of this and a bit of that until he had the dogs he wanted. The breed was "recognized", the studbook closed, and the gene pool has been getting smaller ever since. Can the breed be saved by a cross-breeding program? Who knows, but certainly it is worth a try and there is little to lose. But time is running out.

How many of you just read the last paragraph and thought to yourselves "But breeders will never do it". Really? Not the "responsible" breeders? Not even the "preservation" breeders? Is there nobody who loves this breed enough to save it?

Go back and watch that video of the Doberman dropping dead in the middle of a game of fetch. Where are the breeders - those most devoted Doberman lovers - who will do something about this? This isn't my breed, but it's breaking my heart.

Postscript
If you're thinking that you're glad you aren't a Doberman breeder, you should have a look at the data for your own breed. There are unfortunately many breeds in which dedicated (responsible, preservation) breeders are likewise pursuing solutions by supporting research to study the health condition or searching for causative genes. Huge sums of money are being spent, breeders are becoming experts about esoteric veterinary disorders, and Facebook is burgeoned with groups for information, commiseration, and condolences.

But the path is the same, and the consequences probably are too. There is only one way to cure the diseases that result from inbreeding. Breeders are the only ones that can fix this. The problems have become obvious and undeniable in many breeds: Berners, Goldens, Flatcoats, Irish Water Spaniels, Cavaliers, Akitas, Dogue de Bordeaux, Bulldogs, Scotties, Westies, and the list goes on.

​There are a lot of breeds in trouble, with high inbreeding, low diversity, a growing list of genetic disorders, and plans to start another research study.

Science can learn about the problems caused by inbreeding, but the "cure" for inbreeding will have to come from the breeders. If you want to preserve your breed, this is the problem you need to address.

Go to Are we watching the extinction of a breed? (part 2)

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