What You Need to Know About Purebred Dogs

Educate yourself on the risk factors of breeding purebred canines.

It’s important to know the lineage for any purebred dog you’re thinking of getting. By: Bieniu94

Thinking of getting a purebred puppy?

Then take a few minutes to read this article.

Seriously — it could save you from heartbreak.


Pure Love

When you fall in love with a particular breed, that puppy may carry an increased risk of genetic health problems. For example, think:

  • “Labrador” and hip dysplasia
  • “German Shepherd” and pancreatic problems
  • “Chihuahua” and wobbly kneecaps
  • “Collie” and early-onset blindness

Need I go on?

The reason is that creating the “look” of a breed means mating dogs who share a physical resemblance. But an unwanted consequence is that the dogs are related. If those ancestors share a “bad” gene coding for, say, hip dysplasia, this gets passed down the line along with the breed’s looks.

A complication is that purebred dogs who appear fit and well may carry recessive genes for ill health. These recessive genes then show up when 2 dogs sharing the same gene are bred, resulting in 25% of the litter falling sick with that condition. If your pup is the 1 in 4 who develops debilitating hip dysplasia by the age of 3, then this matters — a lot.

If you’ve suffered the heartbreak of a gorgeous pet who becomes ill with a hereditary health problem, you’ll want to avoid this in future. But how?

Actually, there are ways to predict puppy health and therefore choose from a litter that’s statistically less prone to disease. Here’s how.

Coefficient of Inbreeding (COI)

If you take home one message about genetics, it’s that diversity is good. In its simplest terms, when 2 healthy, unrelated dogs are bred, this gives the best chance of strong, genetically healthy pups.


But the other side of the coin is that breeding 2 closely related dogs magnifies hereditary health problems. Indeed, this risk can be measured and is called the “coefficient of inbreeding” (COI).

We can get as complicated as you’d like about genetics and the COI (homozygous, heterozygous anyone?), but instead, let’s put things plainly.

The coefficient of inbreeding shows how distantly related 2 dogs are. By: Alexas_Fotos

COI and Its Interpretation

The COI measures how distantly related 2 parent dogs are and how many ancestors they share. It is written as a percentage. The lower the number, the less closely related 2 dogs are.

So 2 dogs with a 0% COI are totally unrelated — ideal! But a couple with a COI of 25% would be like breeding brother and sister or father to daughter — not a good idea. A halfway house is a COI of 12.5%, which is like mating grandfather and granddaughter. It’s still not a great idea.

Indeed, you can look at a breed as a whole to see how inbred it is. The UK Kennel Club has a slightly addictive Mate Select app for this where you put in the breed and see its overall COI.

Remember, a large gene pool will have a low COI, while a tiny gene pool has a high COI. In practical terms, a breed with a low COI means it should be easy to find a completely unrelated dog to mate. But a high COI means most of the dogs in that breed share lots of common ancestors.

Here is some of the breed COIs I looked up:

  • Pug: 4.9%
  • Beagle: 9.7%
  • Poodle: 4.3 percent (miniature and toy), 2.3% (standard)
  • Labrador Retriever: 6.5 percent
  • Cavalier King Charles Spaniel: 6.3 percent

What It All Means

OK, let’s say that, unbeknownst to you, the breeder is a cheapskate and breeds closely related dogs together. This increases the chances of the pup having a genetic health problem.

One way of recognizing this is to study the pedigree papers of the parent dogs, but have you ever done that? It’s very complicated.

However, registered breeders have several generations of their dogs listed with the Kennel Club. This means all you have to do is visit the Kennel Club website and in the relevant section enter the pedigree name of both parent dogs, and presto: It generates a COI.

If that figure comes out at a scary 25%, then steer well clear. Indeed, even a 12.5% is bad news, so choose accordingly.

Watch this news item on the problem Bulldogs are suffering because of inbreeding:

The COI Predicts But Doesn’t Guarantee

The COI is a great tool for avoiding inbred pups, since these carry a greater risk of carrying bad genes. However, it doesn’t guarantee a healthy pup (nothing can), but team this up with buying from parents who are screened for genetic disease, and then you’re really cooking.


Do some homework about the breed. Find out which disease they are prone to. Then cross reference this with a database that advises what screening tests are available.

Then look for a breeder who breeds responsibly and has their parent stock screened for those problems. Again, this doesn’t guarantee a rock-solid healthy puppy, but it certainly helps. When you select 2 unrelated, low-risk parents, then things look rosy for a strong pup who grows into a healthy adult.

Of course, those screening tests cost money, so expect to pay more for the puppy, but what price can you put a price of peace of mind?

Useful Sites

To help you find that healthy pup, here are some useful sites:

In short, when sourcing a healthy purebred puppy, find a breeder who screens for hereditary disease. Then pop the parent dogs through an app that checks their COI and only accept a pup from unrelated (or very distantly related) ancestors.

May the patter of tiny paws always bring you happiness rather than heartache.


This pet health content was written by a veterinarian, Dr. Pippa Elliott, BVMS, MRCVS. It was last reviewed April 6, 2018.


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