Health and Your Mixed-breed Dog: Can Science Predict Future Problems?

If you know anything about how dog breeds evolved, you would know that modern dog breeds have been established through generations of selective breeding. Breeders would identify desirable traits, such as retrieving, protection, companionship, herding, etc. They would then breed pairs of dogs that showed the most potential for these features. Over time, very distinct breeds in terms of look, size and behavior emerged.

But there were other unexpected results from selecting for particular traits. While certain traits were bred in, certain diseases were bred in as well. This means at a genetic level, certain breeds of dogs, are more vulnerable than others to certain diseases.

Many diseases are linked to breed identity

For example, German Shepherds are prone to hip dysplasia. Labs are prone to weight problems, and like people, obesity is linked to health problems in dogs. Boxers are prone to certain kinds of cancers – some treatable if they are caught early enough. Dobermans are vulnerable to Dilated cardiomyopathy (DCM) which can be managed with medication. If you own a Doberman, chances are your vet will recommend that you have the annual screenings.


But what if you have a mixed breed dog? If you have a part lab, then you know ahead of time that you will need to focus on weight gain prevention since it is far easier than weight loss for dogs.  If you think you have a part Doberman than you can make sure your dog has an annual screening for its heart because it’s common that owners that have dogs with DCM only find out after their dog has collapsed.

The trouble is, most people try to guess what their mixed breed dog by looking at them. But with the recent advent of genetic testing, science has uncovered some very curious things about what we think we know about our mixed-breed dogs. What we think our dog is by looking at them is often wrong.  Your part lab may actually be part Doberman. You may be watching their diet, and never even think to screen them for their hearts until it’s too late.

Visually identifying mixed-breed dogs difficult

Recent studies comparing visual identification of dogs by people with DNA breed identification show that we can’t identify the predominant breeds in mixed dogs very well. In this study: Comparison of Visual and DNA Breed Identification of Dogs and Inter-Observer Reliability, it was found that for 14 of the 20 dogs, less than half were able to identify the predominant breeds that matched the DNA identification.

Mars Veterinary, who developed the Wisdom Panel genetic test, did the DNA analysis on these twenty mixed-breed rescue dogs (you can see them here).

These participants weren’t just your typical dog owners, either. These were all people involved in dog-related activities such as veterinary medical groups, animal control/sheltering agencies, dog clubs, and regional and national conferences related to veterinary medicine and dog-related activities. Over 900 of them.

But this is not the only study that indicates how wrong educated dog people can be about guessing what breeds a mixed-breed dog comes from.  In another study done in 2009, Comparison of adoption agency breed identification and DNA breed identification of dogs used shelter dogs and shelter workers. The study compared the shelter workers breed identification with DNA breed identification results.  It found that only 4 of the 16 dogs had the identified breed as the predominant breed in the dog’s ancestry. 87.5% of the dogs identified by an adoption agency as having specific breeds in their ancestry did not have all of those breeds detected by DNA analysis. If you have adopted a dog from a shelter, this is important to know.

Dog breed designations have also been used in an attempt to predict future behavior 

– UF Maddie’s Shelter Medicine Program, UF College of Veterinary Medicine.

And finally, data collected in a survey by Dr. Julie Levy with the assistance of Merial Veterinary Scholar Kathleen Croy compared the results of more than 5000 dog experts guessing on 100 dogs with the DNA results. It’s pretty interesting.  While the site doesn’t include statistics of how many guessed wrong, it does show what the top breed guesses were and shows what they actually are.

This leads us to ask: why do we get it wrong?  Why would mixed-breed dogs look so different from their parents or grandparents?

Why do mixed-breed dogs look so different from their parents or grandparents?

Cross-bred offspring dogs often look different from their parents or grandparents because of the number of genes responsible for how they look as a breed. Dogs have approximately 20,000 to 25,000 genes.  Fewer than 1% of the dogs genes influence the physical traits that we would identify with a particular breed. That means that a dog that has 50% German Shepherd in them might look absolutely nothing like one. Especially if that German Shepherd was crossed with another mixed-breed dog.  Small dogs may have large dog ancestry and vice versa. At 1% of genes being responsible for the way a breed looks different from another, it is no wonder we guess wrong so often.

Correctly identifying a mixed-breed dog may help predict both health problems and  behaviour

Without truly knowing what breeds you mixed-breed dog has descended from, you can’t anticipate his or her health needs and vulnerabilities. Getting your dog tested should help you predict future health problems. But there are behavioural tendencies associated with breeds as well that we should be aware of in a mixed breed.

For example, behavior specialist Dr. Ellen Lindell was quoted as saying in the VIN article that, “Since terriers and hounds work independently, they might not be as sensitive to owner cues.”

What this means to a dog owner of a mixed-breed dog is that they will have to work a little harder at setting up a clear communication system. Karen Overall’s deference protocol;

 “No such thing as a free lunch” (NILIF) by Victoria Voith; “Learn to earn” by William E. Campbell, as detailed by Debra Horwitz in Changing the Owner-Pet Relationship or the SAW program in the Dog Aggression System Every Dog Owners Needs book may work really well for these dogs.

Lindell goes on to say, “Herding dogs are ultra vigilant — bred to follow subtle movements and notice all sounds. Inexperienced owners might not give these dogs enough information. Most dogs in the working group were bred to guard, so if a person with a working dog wants an open-door policy, then that person will need to work extra hard to teach the dog that everyone is welcome.”

These behavior tendencies can be accommodated for, but what if you think you have a lab-shepherd cross that is actually a terrier cross?  You might expect them to be much more in tune with you because after all, aren’t both labs and shepherds smart?  Aren’t they used as guide dogs, after all? Not knowing the truth potentially sets up dog owners to have unrealistic expectations.  These unrealistic expectations can affect the human animal bond.  It might even effect whether the dog is relinquished down the line.

DNA and Dog Aggression

Currently the DNA tests that you can buy do not tell you if your dog has a particular gene or genes for aggression. Nor does it tell you why your dog is aggressive.

Current genetic research suggests that the predisposition for aggressive behavior is likely related to a combination of genes, and not any one in particular, although there are some genes identified as having a greater influence than others.

There is some statistical research on breeds suggest that certain breeds may be statistically a little more likely to show certain kinds of aggression than others, so from that perspective the DNA tests you can buy may be helpful in combination with that knowledge. You might head over to do the C-BARQ survey to get more information and compare your dog with others.

However given the variability in the scores with each breed group, it’s not useful to determine if a dog is likely to be aggressive on breed alone. In all cases the majority of dogs in each breed group don’t show the inclination towards aggression.

At best, if your dog is aggressive, perhaps realizing there may be a genetic component will ease your frustration in working with them or whatever guilt you might feel for the fact your dog is aggressive or reactive (and ideally, motivating us to work harder at avoiding the circumstances the cause aggression in the first place). Understanding how likely your dog is willing to learn and so on may be helpful to you in treating your dog’s aggression. In time, we hope genetic research can provide us with even more answers.

How do DNA breed identification tests work?

Leading canine DNA testing such as Embark or the Wisdom Panel requires you to collect a sample from the inside of your dog’s cheek with a swab and then you send it back to them.

After analysis you given information showing the ancestry of your dog by breed, as well health information. It can be done on puppies, too. If you choose to do this make sure you follow the directions in getting a good sample.

In the lab the commercial tests look at genetic markers within the genome (a genome is found in cells and includes the complete set of DNA). These markers are known as single-nucleotide polymorphisms (SNPs – pronounced “snips”) which are small variations in the genome. These markers are called “signatures” and are particular to each breed. Some breeds are more difficult to identify than others because portions of their signatures resemble others (the Chihuahua and some mastiffs, for example). The more unique the breed is, the easier it is to identify via DNA. The more mixed a dog is – in other words, a dog who has been bred from generations and generations of mixed-breed dogs, the more challenging it will be to identify accurately.

Obtaining and administering the test

Getting and administering the test is easy. Check out buying DNA tests for dog – what to know.

If you are interested in learning more about genetics and cross breeding, you might also be interested in Genetics and the Social Behaviour of the Dog by Scott and Fuller. This ground breaking study done approximately 30 years ago is considered to be the landmark study in genetics. It shows how many of the offspring dogs look more like other breeds than they do their parents.

So will you find out what your breeds your mixed-breed dog descended from? And if so, will you believe it?


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