Pure-bred, or 'pedigree' dogs are more likely to have various health issues, because the more you breed the dog (to be pure), the more their genetics get...messed up due to the fact that this is a case of in-breeding.
What is the big deal with in-breeding?
Well, it causes your recessive genes to eventually become dominant ones. These recessive genes can carry traits from one generation to the next. Selecting the right mate for a dog where such recessive traits are not apparent, or are believed to not have the trait guaranteed, can lead into the diversification of genes. Every sexually-reproducing creature, which includes humans of course, must promote the diversification of genes by mixing with those who are not so closely, even directly related. Diversity wins, demonstrably so, again and again.
Anyway...
Just some dogs that have some major health issues because of how they're bred (especially if pure-bred, which is a euphemism for in-breeding, which only makes these issues worse with each generation):
- The English bulldog
- The Pug
- The Norwegian Lundehund
- The Bull Terrier
- The Basenji
Then there's breeds with certain traits that persist due to breeding (sometimes in-breeding, others because of deliberate selection of traits, etc.):
1) The German Shepherd: hip dysplasia is the most prominent issue, and most visible (the lowered hips).
There's at least one breeder (seen here: https://www.facebook.com/TsaheyluShepherds/) who is working to rectify the issues that have been plaguing this breed for generations.
2) The Dalmatian: prone to deafness
A study with 26-years of data shows that there's an effort with some breeders to decrease the incidence of deafness, by selecting mates that do not exhibit this trait. In-breeding has allowed the gene to proliferate more often in this familiar breed. (https://www.veterinary-practice.com/.../new-study-reveals...)
3) The Boxer: many of these dogs have heart disease
Earlier this year, research at the Cummings School yielded some promising clues into reducing the predisposition of this breed for getting heart disease. The disease in question is called "arrhythmogenic right ventricular cardiomyopathy", or ARVC, a condition that humans can get as well. It's a condition wherein fatty tissues replace the normal muscular tissues of the heart, which can interrupt the electrical signals the heart needs to function. You sometimes wouldn't know that your dog(s) of this breed have it until it's already dead – sometimes suddenly so.
Read more on that study here: https://now.tufts.edu/.../mending-hearts-beloved-dog-breed
...and more where both lists came from.
Encourage the diversification of the genes of dog breeds. If you want a dog:
1) Adopt a dog from a shelter or owner who cannot keep said dog for whatever reason.
2) Jumping off of the previous option, give senior dogs a chance. They may not have very long to live, and could have health issues, but they deserve happiness like any GOOD BOI.
3) Find a responsible breeder who tries to correct the problems with pure breeds, and takes care of their dogs & their puppies. Never wean a puppy before 3-4 weeks of age because that often leads to its own set of issues down the road. A place like Kijiji is actually fine for looking to adopt, since the site has had to follow enforced guidelines over the years.
Still issues with trust and quality of breeding programs, but how can you absolutely avoid that in this world?
It can be difficult due to a variety of reasons, but if more people educate themselves about the downsides of espousing "pure breeding", then they can help endow future generations of the various degenerating (through no fault of their own) breeds with a brighter, healthier future.
