Are Mixed-Breed Dogs Healthier?

A mixed breed dog relaxes with a Labrador and a golden retriever on a sofa.
Who’s healthier?

A recent blog post by Dr. Stanley Coren mused about “hybrid vigor” or the notion that mixed-breed dogs are healthier — or, at least, less prone to genetic diseases — than purebred dogs. I decided to read the full study he referenced to learn more.

A large group of researchers, mostly Finnish, studied a huge sample of dogs: more than 83,000 mixed-breed and more than 18,000 purebred dogs of 330 different breeds. They analyzed the dogs’ genotypes, looking for 152 different genetic markers that underlie hereditary diseases.

They quickly narrowed down the study: Of the dogs with a faulty gene, 96 percent had one (or more) of a group of 30 genetic markers or “disease alleles.” They narrowed further, selecting the nine most common markers, which all appeared in multiple purebred breeds as well as in mixed-breed dogs in the sample.

Several findings might be interesting to dog owners:

  • Mixed-breed dogs are as likely or more likely to carry some genetic variations linked to diseases than purebred dogs.
  • But purebred dogs are more than twice as likely to actually have a genetic disease.
    That makes sense; the number of purebred dogs who are actually bred is quite small, and many are bred to dogs from the “same lines” — relatives, even very close relatives. Within a closely related population, the likelihood of dogs sharing a recessive gene is much higher than in the broad population of mixed-breed dogs.
  • Deeper study of individual mixed-breed dogs who carried rare genetic variations found that, even when the dogs exhibited symptoms of a genetic disease, these individual dogs were only diagnosed after the owners had the results of the genotyping.
    That also (sadly) makes sense: The vets didn’t suspect that the mixed-breed dogs had rare, usually breed-linked, genetic diseases.

The question of “hybrid vigor” is nuanced, since the dogs are likely to be carriers but less likely to suffer the diseases, but I’d argue that mixed-breeds are healthier.

In his post, Coren also points out that another common belief — that breeders frequently breed dogs known to be carriers or even sufferers of a disease — is unfounded. Many breed-specific genetic diseases have become extremely rare or have been eradicated — due to careful breeding. Some breed clubs forbid breeding of carriers of known genetic diseases.

The researchers are sharing their data; they’ve created the free My Breed Data database, where anyone can search for information on genetically linked diseases.


The Price of Being a Hero

Cali had a terrible, horrible, no-good, very bad day.

It all started in the evening, when, as Cali sees it, her mom attacked her with a machete, leaving her paw a bloody stump. It’s true that, for the first time in her life, I nicked a nail, clipping a bit too short. I saw a total of three drops of blood. Cali ran outside and sulked, then came back in and put herself to bed. She soon fell asleep, holding paws with her now disarmed, and very sorry, mom.

Then, in the morning, I faced down the stares of two disbelieving goldens as I failed to serve breakfast on time. Unable to take the pressure, I fled to the relative safety of the gym. On the way home, I got confirmation that Cali’s annual appointment for the Morris Animal Foundation’s Golden Retriever Lifetime Study would take place as scheduled.

Cali’s day was going downhill, fast.

Cali was initially delighted by the impromptu ball game when I got home … until she realized that she was being played (with). While big-sis Jana was getting breakfast.

Then, in Cali’s mind, her mom truly went nuts. She started chasing poor, hungry Cali around the yard wielding a paper plate. Every time Cali squatted, Mom shoved that darn plate in places that really shouldn’t be mentioned in a family-friendly blog. No way was Cali going to pee on that thing! They then walked up and down the street, with Mom still carrying the plate, and Cali thoroughly sniffed everything. She even faked Mom out a few times. Cali sure showed Mom, though: No pee.

Finally, things started looking up. Cali was excited that she got to go in the car with me, and Jana had to stay home with her super-duper treat toy. Hey, wait a minute …

At the vet’s office, Cali danced in, eager to see all those nice people who would ply her with cookies and tell her what a good girl she is. She got her wish: lots of attention, but … no cookies. Instead, they stuck her with needles and drained some of her blood. They cut some of her hair. And they tried to suck out some pee with a syringe, but she fixed them, too. No pee. Then she got some cookies. Finally!

Next, we got to go out for lunch. At last; something fun for Cali! Cali finally got her breakfast and a big bowl of water, and she got to say HI! to about 20 people on that patio. They all told Cali that she was a good girl. Except the one lady who said she was a good boy. A boy? With those long blonde eyelashes?

Then … oh, no! Back to the vet! Poor Cali got poked and prodded some more; the vet techs scraped off the edges of her toenails (no blood this time), gave her a shot, and finally got some pee, and the vet looked into her eyes with a very uncomfortable bright light, examined her teeth and her ears, took her temperature (she didn’t like that part at all), filled out an endless questionnaire … and pronounced her perfect. And they all gave her cookies, of course. Lots of cookies. She didn’t plan to tell Jana that part.

When we left, we took two huge packages — which smelled very much like Cali — and raced to the FedEx dropoff. Just in time. Off the samples went, to join those of 2,999 other golden retrievers who go through this exhaustive exam every year as part of the study.

Cali, along with two of her brothers, is one of the Morris Foundation’s golden retriever “heroes,” hero #608, to be exact. They’ll each give up a day every year, throughout their entire lives, as well as copious amounts of samples, so that the study researchers can try to figure out what causes cancer in golden retrievers. And other dogs. And what can be done to prevent it. From there, who knows who else Cali and the other heroes will help.

Best of all, we got home in time for dinner (and a trip to the park)!