We are happy to see that there is a lot more discussion in the news lately around canine health, and how some of our breeding practices are producing some quite unhealthy dogs. You may have heard people mention that crossbred dogs are healthier than purebred dogs. Is this true? And why are some dogs unhealthy at all? Are there any solutions?

Crossbreed and Purebred Dogs

Firstly, what actually is the difference between a crossbred and a purebred dog? We’ve spoken about this before. In the late 1800s, it became fashionable to show dogs at competitions. So it was necessary to start regulating and categorising dogs into different standard breeds for judging. This became the basis for the UK Kennel Club. 

Today, purebred and pedigree dogs must be bred from parents of the same breed – to be a purebred Dalmatian, both parents have to be pure Dalmatians. Pedigrees have ‘proven’ lineage with the UK Kennel Club. But for even the most pedigree dog, its lineage is only on record as far back as the UK Kennel Club was formed; all dogs are of the same species and share many of the same genes from common ancestors. Nevertheless, purebred and pedigree dogs are generally bred from a very small population (we can’t grow this population, or the purebred/pedigree label would be lost) which means very little diversity, often leading to problems. More on this later.

On the other hand, crossbreeds are what they sound like – a mix of different breeds. Mongrel, mixed breed, mutt: these are all terms for a crossbred dog. One of the most well-known is the cockapoo. There is no standard definition, but crossbred dogs are generally intentionally bred to be of a certain mix (like cockapoos). Whereas mongrels are just mixes with no specific desired outcome. But the long and short of it is if a dog has multiple breeds in its lineage it is a mixed breed dog.

Genetics and Inbreeding

Let’s take a quick detour into genetics. When animals breed, the offspring receives half their genes from their mother and half from their father; each gene forming a pair with the corresponding gene from the other parent. Genes define your traits. If you carry the genes for brown eyes, you will express the genes by having brown eyes. Simple!

However, it gets more complex when recessive and dominant genes come into play. Some genes are more dominant than other genes and will always be expressed. Recessive genes can only be expressed if both genes in the pair are recessive. In humans, brown eyes is a dominant trait and green eyes is a recessive trait. If either one or both eye colour genes in the pair are brown, your eyes will be brown. You can only have green eyes if both genes are the recessive green gene. It is possible to carry one gene for green eyes and one for brown eyes (you would have brown eyes as it is dominant). This is why parents who both have brown eyes can produce children with green eyes. If both the mother and father give the child their recessive green eye gene, the gene can be expressed to produce green eyes.

(OK, yes, it can be more complicated than this because of phenomena such as epistasis, but that’s the gist of it).

So this is all very interesting, but why is it relevant? 

Because dominant traits are so dominant, they tend to be more common than recessive traits. However, if a small population breed together, it allows recessive genes to be given to offspring more often. Over time, this leads to more and more offspring with both recessive genes, allowing them to express the recessive trait. Many recessive genes are harmless, like green eyes, but some are quite harmful and can result in genetic deformities. Cystic fibrosis is an example of a human disease where if two people, carrying the recessive cystic fibrosis gene, have children, there is a chance their child could get both cystic fibrosis genes and have the disease. If a small population of humans who carried the cystic fibrosis gene kept having children with each other (inbreeding), it is likely that cystic fibrosis will be a lot more common than in the general population.

This is the reason why (apart from moral reasons of course), inbreeding in humans is generally frowned upon. It increases the risk of producing children with nasty genetic diseases. Just ask Icelanders who have an app to check if a potential partner might be related, due to their small population! Yet we seem to have no qualms about doing this with dogs. In fact, we laud it and call them purebred or pedigree…

Vetster option 01 (Blog)

Purebred Problems

So as we have hopefully demonstrated, small populations inbreeding with each other results in an increased occurrence of recessive traits which are often harmful. In purebred dogs, this is oh so very true.

A number of severe genetic diseases are common with purebred and pedigree dogs; directly as a result of inbreeding within small populations. Some examples include heart disease in Cavalier King Charles spaniels; CDRM in German Shepherds; spinal issues in Dachshunds, and cancer in Boxers. Most of these diseases are incurable and incur considerable veterinary bills to manage. The life expectancy of these dogs are often much lower than normal. 

It gets worse when you take into account we sometimes select certain traits on purpose, even if they are harmful. Pugs and similar short-faced dogs have terrible breathing issues as a result of their ‘cute’ small noses. German Shepherds hip dysplasia is worsened by selecting for a sloping back. Shar-Peis are desired to have skin folds that result in infection. This kind of breeding has resulted in some of our most beloved dogs. But it has also introduced a slew of problems into animals that should never have had them.

On top of this, we know that even without diseases, purebred dogs tend to live up to a year less than mixed breed dogs.

Are Crossbreeds All Healthy?

So it sounds like purebred dogs aren’t always very healthy. Both because of intentional trait selection and the increase in genetic diseases. Does that make mixed breeds healthier? Unfortunately, we have to say not always. 

While many genetic diseases are more common in purebred dogs, many are equally as common in mixed breed dogs, such as some cancers and heart diseases. One study even found that cranial cruciate disease may be more common in mixed breed dogs. 

Furthermore, where purebred dogs with selective breeding can sometimes improve a dog’s health (more on this in a bit), as most mixed breeding is unregulated, it can be a lucky dip what you end up with – the puppies could all be healthy or all diseased. Not knowing the health of the parents makes this riskier.

Finally, there is even some evidence that new crossbreed dogs, like cockerpoos and puggles, could be just as unhealthy as purebred dogs. A study found that breeding new breeds makes it more likely you will introduce genetic diseases from both breeds, rather than remove them. We are already seeing this with cockerpoos, such as progressive retinal atrophy (blindness) from both parents. This is even more of a problem when the diseases we are concerned with – like hip dysplasia, for example – aren’t controlled by a single gene. But by many hundreds all working together.

So will genetic diseases always be a risk of breeding?

Overall it seems that whether dogs are bred from a tiny stock of purebred dogs, or randomly bred from a large population, it can result in genetic diseases. In all honesty, this is a human-created problem due to such practices, and a lot of work must be done to reverse this trend. Do also consider that a dog’s health is a product of its environment as well, and any dog can become unhealthy without proper care.

Enough negativity, let’s talk solutions.

The UK Kennel Club has received a lot of blame for historical breeding practice. But they are taking steps to try and ‘fix’ certain breeds (though arguably a lot more must be done, as breed standards are often still incompatible with health). The Kennel Club recommends that breeds at risk of hip dysplasia are hip scored by a vet (via x-ray) to assess how severe it is. And how likely it is that any puppies would have hip dysplasia. By only allowing breeding of dogs with healthier hips, this will slowly reduce the incidence of hip dysplasia. A similar scheme for flat-faced dog breeding has been trialled in The Netherlands. Though not yet by the UK Kennel Club. The UK Kennel Club does offer an Inbreeding Coefficient calculator that can be used to determine how inbred the puppies of two registered dogs might be.

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There are also a number of genetic tests offered by vets that can screen dogs for certain diseases. If your dog carries genes for these diseases, you can be responsible and only breed with dogs that do not carry the gene, or preferably not at all. Again, this will help remove the disease genes from the populations. If your dog is of a particular breed, ask your vet what genetic tests they recommend before breeding.

One of the advantages to pedigree dogs is having a proven lineage. If there has been a long line of healthy dogs with specific diseases not present, you can be more confident a new offspring will also be healthy. The record would work in the same way to help you avoid dogs with a history of genetic problems in their lineage. However, genetics is a science we have still not yet mastered, and predictions are never 100% accurate. 

What’s the Verdict

Regardless of purebred or mixed, the human desire for so many varied dogs has caused a lot of issues. And led to some quite poorly puppies. It is still up in the air on whether purebred or crossbred dogs are healthier, and in all likelihood it probably depends.

If you are looking to breed, or in the market for breeding, there are a number of steps you should take to ensure your puppy is the healthiest it can be. 

Only breed if you are a (or purchase from) registered breeder

This will help reduce the incidences of random breeding that can result in poor matches and sickly puppies. 

Do perform as many genetic and other health tests possible before breeding 

Research the breed, find out what the health issues are. Utilise Kennel Club resources to reduce the risk of producing unhealthy pups. Many schemes are open to non-purebred or -pedigree dogs as well, so everyone can benefit.

Finally consider the breed of dog you want. 

Admittedly, almost every breed has some health issues (thank you inbreeding), but some are certainly worse than others. Short-faced breeds like pugs, Frenchies, and other bulldogs are probably the most topical at the moment. It is great to see stories in the news of people breeding ‘retro pugs’ with longer snouts. This shows how breeding can be a power for good and reverse the unhealthy changes! Consider dogs like this over flat-faced dogs that cannot breathe (or better yet dogs with normal snouts anyway!). 

We hope this article has shed some light on purebred vs crossbred health, genetics. And some of the ways we can improve dog health. Dogs are wonderful creatures, and it is unfair so many are suffering because of human greed. We hope the tide is slowly turning back to healthy function over unhealthy style. As always, ask your vet if you need any further advice.

Summary:

  • Many genetic diseases are more common in purebred dogs
  • Other genetic diseases are just as common in crossbred dogs
  • Cross breed dogs tend to live longer than purebred dogs
  • Unregulated crossbreeding can lead to issues just like pure breeding does
  • Any dog can be unhealthy depending on its parents 
  • There is no overall verdict on which is healthier
  • When purchasing a dog, focus on the breeder being registered, the parents having had testing, and not purchasing certain breeds, rather than whether it is pure or crossbred

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