Are purebred dogs always inbred dogs?
Do inbred dogs suffer?
And what is inbreeding anyway!
We dig down into the controversy over pedigree dogs and pure breeding.
Purebred vs Inbred Dogs
You may have heard that mongrels are far healthier than pedigree dogs, and that pedigree breeds are all doomed.
You may also have heard that this is utter nonsense, and that pedigree dogs are more healthy than mongrels or crossbreeds.
So who is right?
The truth lies not in rumors, objections, and shocking headlines.
It is in a basic understanding of what happens to a breeding population, when we humans take control of it.
What is inbreeding?
Inbreeding happens when individuals who are closely related produce offspring together.
When we talk about inbreeding in a population or group of individuals, we normally mean that this is occurring on a regular basis, rather than being a ‘one-off’ event.
Usually many members of the group in question are quite closely related to other members of the same group
In nature, this can happen because a group becomes isolated geographically.
On an island for example.
Among humans it can happen for cultural reasons too.
For example, there are traditions of cousins marrying one another in some cultures.
In our purebred dogs, it has happened because humans chose to breed from closely related dogs.
But what exactly do we mean by closely related?
How close is too close? And why?
If your eyes glaze over when you hear words like coefficient you are not alone.
But if you spend any time at all around dogs, you are going to hear this word a lot more in the next few years.
It is actually a way of describing or defining exactly how closely related two individuals are.
A high COI (coefficient of inbreeding) means a close relationship.
A lower COI means a more distant relationship.
So for example, mating a brother or sister dog would result in a COI of 25.
Cousin to cousin gives you a COI of 6.25
Lower COI is a better COI
The coefficient of inbreeding is a really useful tool for anyone breeding dogs.
But it’s also helpful if you are looking for a puppy.
Because scientists have now discovered that dogs with higher COIs are more likely to get sick.
Specifically, they have shown that when the COI of any mating exceeds 5%, puppies are at increased risk from the adverse effects of inbreeding.
The Kennel Club in the UK is beginning to publicly recognize some of the problems caused by inbreeding.
It has now has information to help breeders and puppy buyers make better choices.
If you are in the UK or own a British dog, you can find your own dog’s COI by using the calculator on the Kennel Club website
Now let’s find out what those adverse effects are and why they happen.
Why is inbreeding bad?
Genes carry the code or instructions for every aspect of how your dog will look and function.
And aspects of his personality too.
As with everything in this world, sometimes genes get broken or don’t work.
Or are faulty and work in the wrong way.
This is when things can start to go wrong.
The genes of inbred dogs
Fortunately, your puppy gets two copies of each gene.
One from his mom and one from his dad.
Usually a working gene overrides or switches off the broken one.
There are usually not too many copies of a faulty gene floating about in the general population.
So this switching off works well.
But the more closely related those individuals are, the more likely they are to share the same faulty gene.
When faulty genes meet
When the parents are closely related, their puppies will have an increase chance of inheriting a faulty gene from each parent.
And an affected puppy with two faulty copies of the gene will have no working gene available to over-ride them.
The effects of that gene are then free to rampage around the dog, in some cases with devastating consequences.
Dogs before selective breeding
In a healthy population of dogs, if a puppy gets a broken gene from his Mom, it will probably be paired with a working gene from his Dad.
The puppy will be no worse for carrying the faulty copy his Mom gave to him.
This is the beauty of ’sexual’ reproduction.
A system where two parents are needed to create each amazing new individual.
Some people are surprised to discover that not all animals reproduce in this way.
But all mammals do, and that include our dogs.
Messing with the system
So we have this perfect, or nearly perfect system.
One where faulty genes are masked by healthy ones.
Broken or disease causing genes remain hidden and harmless within the population.
These ‘duds’ are carried down for generation upon generation, for the most part doing no harm.
In fact these ‘hidden’ broken genes even occasionally come in handy.
When the environment changes for example, a different type of gene can actually help an animal adapt to new circumstances.
But how have things changed for our modern dogs?
Dogs have been living alongside us, sharing our hearths, our food, and our fortunes for many thousands of years.
In order to reliably produce dogs that are more useful, we have engaged in selective breeding.
Mating dogs together that are share the qualities that we like best.
And breeding different types of dogs for different roles.
Dogs for different roles
Selective breeding has created the amazing variety of dogs we see around us today.
It has given us our beautiful and amazing pedigree breeds.
And that doesn’t have to be a bad thing.
A pedigree, by the way, is strictly speaking an ancestral record – a written or memorized family history.
It is not the same as ‘purebred’ though the two terms are often used interchangeably.
For much of the history we have shared, this selective breeding practice has little harm to our dogs.
So what changed?
What does purebred mean?
What changed for dogs, just a century or so ago, was this emphasis on pure breeding.
The idea that pure breeding would be a great way to make our dog breeds even better.
An idea that resulted in the decision to genetically isolate groups of dogs from one another by introducing the concept of the ‘closed register’
Purebred means only mating animals that belong to the same strictly defined group or breed.
Whereas previously, dogs had been mated to one another selectively.
Based on qualities and appearance, rather than based on their ancestral record or relatedness.
One by one, over the space of a few decades, the pedigree registers were closed.
Purer isn’t necessarily better
Ensuring that Labradors could only ever be mated with Labradors, Beagles with other Beagles, Collies with other Collies.
And so on.
And our dog breeds have been isolated ever since.
Of course some dogs have always been mated outside of these registers, and interested in mixed breed dogs is growing again.
But still, for a hundred years or so, a huge majority of our classic dog breeds have been largely isolated from one another.
The effects have been far reaching.
The journey to inbreeding
What was once a very large population of dogs has now become many much smaller populations.
And each of these small populations is vulnerable to the effects of genetic drift.
Let’s explain what that is before we look at some of the other problems that can arise through inbreeding.
Disadvantages of selective breeding: genetic drift
Selective breeding can cause problems when those in control don’t understand how closely related animals can be before the risks of adverse effect kick in.
How a population of animals can permanently lose genetic material.
Why it matters if they do.
It is a source of great confusion and misunderstanding amongst dog owners.
And amongst dog breeders too.
Every population of animals is subject to a phenomenon known as genetic drift.
It basically describes the way that a gene pool diminishes because individual genes are constantly being lost and not replaced.
Genetic drift is simply the result of ‘chance’ or ‘luck’.
Genetic drift causes gene loss
By pure chance, some individuals in a population may not get the opportunity to breed.
They may be killed in an accident for example.
Or in the case of dogs, they may be deliberately prevented from breeding.
When these individuals die, their genes die with them because they have not been passed on.
And among those lost genes may be unique genes that don’t exist anywhere else.
They are gone forever.
Losing genetic information
One of the adverse effects of genetic drift is the permanent loss of genetic material from any given population of animals.
If a population becomes isolated, the process of genetic drift can become a serious health issue.
No more genes can be added, unless that population is once again opened up and exposed to a larger and different population of animals from the same species.
Meanwhile, genetic drift inexorably reduces the genetic material available to the remaining population
The smaller the population, the more quickly the impact of genetic drift will be felt.
In domestic dogs, repeated matings between close relatives has long been accepted as normal and even desirable.
It even has its own name – line breeding
Line breeding often involves mating grandmother to grandson, or even father to daughter.
Although it was given a different name, all line-bred dogs are inbred dogs.
This was completely acceptable twenty years ago, and is still practiced by some dog breeders today.
So why do they do it?
The answer is that line breeding helps to fix great qualities in a dog.
If you have an outstanding dog with outstanding qualities, you are most likely to perpetuate those qualities by mating that dog to another individual who shares them.
And the dog most likely to share them is probably going to be a close relative.
Dog breeders were unaware that what they were doing was not only bringing together genes that produced great qualities.
They were also bringing together genes that produced nasty problems.
Inherited diseases for example.
Unfortunately, this whole problem has then been greatly exacerbated by another selective breeding issue that has got much worse in our increasingly technological age.
And that is the over use of popular sires
A very popular pedigree dog breeding practice involves the prolific use of popular sires.
Any dog that wins an impressive title, in the show ring or in a sport or activity, is likely to be in high demand as a stud.
This favoring of specific breeding animals in purebred dogs has meant that many members of a breed were then excluded.
Left out of the gene pool.
After all, it is understandable that the owner of a female dog is going to seek out the most talented father for her puppies.
It makes the puppies easier to sell and the breeder hopes to confer some of the father’s qualities on his offspring.
This tendency for a few members of the dog population to be bred from extremely heavily.
While others are not bred from at all, works with genetic drift to remove yet more genetic material from the gene pool of the breeds concerned
And with the advent of artificial insemination, there are no longer geographical constraints on how many puppies a champion can father
You can read more about that issue in this article: The Pox of Popular Sires.
Purebred: meaning breed the best to the best?
You may have heard the mantra “breed the best to the best, spay and neuter the rest”
This concept is widely acknowledged as being the ‘responsible thing to do’ in terms of dog welfare and health
There is also a stigma attached to home breeding and those wanting to have a litter of puppies from their bitch are often strongly advised not to to so.
They may be described in derogatory terms such as ‘backyard breeder’.
But the limitations this gives to the gene pool do serious damage all by themselves.
Inbred dogs and their health problems
When a small population of animals becomes cut off from other animals of the same species, health issues begin to rise
Studies have shown that fertility, and litter size are also adversely affected when populations are isolated in this way.
And that longevity is diminished, sometimes greatly diminished in some of our pedigree breeds.
Some breeds consist largely of inbred dogs and have such small populations now that their future is at risk.
Yet still the registers remain closed.
And more inherited diseases will spring up as more faulty genes get together.
But that isn’t the only problem…
There are also breeds of dog where selective breeding for a particular type has been taken to extremes.
You can now buy puppies who will grow into dogs without muzzles.
A part of the canine body that is essential for cooling and effective breathing.
We have breeds like Bulldogs that are born sick and die sick, just a few years later, and often suffer greatly in between.
And yet other breeds that have been bred with such stunted legs that the vast majority of them will suffer from agonizing spinal problems.
You can avoid some of these problems if you take these issues into account before you buy a puppy.
Finding a healthier puppy
You can look for a breed with a generally low COI.
And for an individual litter of puppies with a low (for the breed) COI.
Choosing a litter bred from a relatively unknown sire may help.
Look for certificates or health clearances for the diseases that are known to occur in that breed.
Avoid puppies that have been bred with abnormal body structure – these often cause distressing (and expensive) health issues.
But this won’t necessarily help you avoid trouble.
The future for inbred dogs
Many population biologists today are very worried indeed about the long term effects of our current breeding practices.
- inbreeding of purebred dogs
- overuse of popular sires
- restricting breeding animals, and those who become breeders
- breeding dogs within closed registers
What can we do?
Genetic drift is a one-way street.
All the genes that will ever be available to a breed of dog is determined at the point at which the breed register is closed.
At the point of ‘closure’ that breed becomes effectively an island population and the genetic material within it can only be reduced.
And the smaller the gene pool, the faster genetic drift may act on the population with potentially disastrous effect.
If we care about the future of our pedigree dogs, we need to seriously consider what effect the closing of the pedigree registers has had on their health.
We need to recognise that turning a large population into many very small populations, may not have been such a great idea after all.
Unfortunately, it has been very difficult to get people to recognise that this is an issue, let alone bring them to the table to discuss it.
Is pedigree good for dogs or bad?
You may think from what I have written that I am against the breeding of pedigree dogs.
But actually, in principle, I am not.
Pedigree dogs don’t have to be inbred dogs.
I am however acutely aware of the risks of isolating groups of dogs from one another.
Aware of the need to discuss the viability of closed registers as a practical long term breeding strategy.
Human beings have gained many benefits from breeding animals with predictable appearances and characteristics.
We now have some extremely useful, beautiful and desirable companion and working dogs as a result of the breeding practices that have been widely adopted over the last hundred years.
But there is a cost to making more inbred dogs. And we need to consider it!
Many pedigree breeds of dog have some serious health problems that affect a significant proportion of the population.
Breeds like the Cavalier King Charles Spaniel.
Inbred dogs – is the price too high?
We do need to think hard about the price our beloved dogs may be paying.
The cost for the benefits we gain from being able to produce dogs which are predictable in appearance and temperament.
There are already grave concerns about several of our popular breeds.
Unless our registers are opened up, it is likely that the accelerating loss of genetic material will continue to worsen and affect more breeds in the future.
The future for inbred dogs
Obviously we want to retain the benefits of producing our favorite breeds and to preserve their characteristics for our children and grandchildren to enjoy.
And it is entirely possible to do this with the careful and judicious use of outcrossing
It may be that breeding within closed registers is simply not sustainable in the long term.
And this is something that we need to be talking about more widely.
Sooner, rather than later.
Much of this information is only just becoming more widely understood and discussed.
There are many issues to consider, much to learn, and to understand.
There is no doubt that those who have influence over our dog breeders (including breed clubs and the Kennel Club) may have to act to ensure the health of our pedigree dogs, within the next few years.
Indeed it is possible that for some breeds, like the lovely spaniel in photo above, it may already be too late.
We can only hope that those with power over breeding practices will rise to the challenge and make what may be unpopular decisions where necessary.
If you are a puppy buyer you can vote with your feet.
Put pressure on your Kennel Club by asking them to consider outcrossing in breeds that are in an unhealthy condition.
It can and has been done in several countries now.
And needs to be a more widespread and frequent practice.
If you are a breeder, you have the power to influence the future health of our dogs.
It is therefore crucial that you understand the principles of population genetics.
The Institute of Canine Biology is a great place to begin, and this article in particular is a good place to start.
How about you?
Are you concerned about the health and future of our pedigree breeds?
Would you like to see pedigree registers opened up and a certain amount of cross-breeding permitted?
Or do you think that would be a step too far?
Can you think of other ways in which we could preserve our breed characteristics without losing even more genetic material?
Let’s talk about this!
References and further reading
- Dobson J.M “Breed-Predispositions to Cancer in Pedigree Dogs” Veterinary Science 2013
- Asher et al “Inherited defects in pedigree dogs. Part 1: Disorders related to breed standards” Veterinary Journal 2009
- Gresky C, Hamann H, and Distl O “Influence of inbreeding on litter size and the proportion of stillborn puppies in Dachshunds” Berliner und Munchener Tierarzliche Wochenschrift 2005
- Collins et al “Getting priorities straight: Risk assessment and decision-making in the improvement of inherited disorders in pedigree dogs” Veterinary Journal 2011
- Rooney N. “The welfare of pedigree dogs:Cause for concern” Journal of Veterinary Behavior 2009
- Adams V, et al “Methods and mortality results of a health survey of purebred dogs in the UK.” Journal of Small Animal Practice 2010
- Dobson J et al “Mortality in a cohort of Flat-coated Retrievers in the UK” Veterinary and Comparative Oncology 2009
- Egenvall A et al “Mortality in over 350,000 insured Swedish dogs from 1995 – 2000. Breed specific age and survival patterns and relative risk for causes of death” Acta Veterinaria Scandinavica 2005
- Farrell et al “The challenge of pedigree dog health:approaches to ocombating inherited disease” Canine genetics and epidemiology 2015
- O’Neil et al “Longevity and mortality of owned dogs in England” Veterinary Journal 2013
- Packer et al “How long and low can you go? Effect of conformation on the risk of thoracolumber intervertebral disc extrusion in domestic dogs” PLoS ONE 2013
- Marsden et al. Bottlenecks and selective sweeps during domestication have increased deleterious genetic variation in dogs. Proceedings of the National Academy of Sciences USA 2016