One of the most desirable traits about a modern pug is its double curled tail. This is actually a genetic defect, and if severe enough it can actually lead to paralysis. Pugs did not originally have this double curve tail. They also have a host of breathing and respiratory problems.
The Basset Hound has gotten lower, has suffered changes to its rear leg structure, has excessive skin, vertebra problems, droopy eyes prone to entropion and ectropion and excessively large ears.
German Shepherds were originally medium-sized dogs with no slope to their back. Now they have shorter hind legs and are about 30 pounds heavier than what they used to be. There used to be a time when a German Shepherd could jump over an 8.5 foot wall.
If any breed has come to signify what can go wrong with selective breeding, it is the English Bulldog. Pretty much every health problem you can think of in a dog, they are plagued by. The median age for an English Bulldog is 6.25 years according to a 2004 study by the Kennel Club. Their sheer mass alone makes mating and birthing almost impossible without medical intervention.
Dachshunds bodies have been elongated which gives them the highest odds of any dog to develop intervertebral disc disease. Their legs have been shortened so much that there is barely any clearance between them and the ground anymore.
Bull Terriers have changed dramatically in 100 years. Selective breeding has caused them to have teeth problems, skin allergies as well as compulsive tail-chasing. Not to mention the deformed skull.
Doberman’s are very prone to something called Cardiomyopathy which is an enlarged heart. Another condition that is the result of selective breeding is cervical vertebral instability. This is caused by a malformation of one of the vertebrae in the neck which can lead to excessive pressure on the spinal cord. This can cause weakness in the back and lack of coordination in the hind quarters.
Originally bred as a working dog, you won’t find many of these dogs doing that anymore. Overheating is a major concern for these very large animals and their workload must be closely monitored. Their large size also makes them more prone to hip and elbow dysplasia. Cardiomyopathy is also something Saint Bernard owners need to be aware of, as well as certain kinds of cancer such as Osteosarcoma.
The flattening of a dog’s muzzle is almost never a good thing. In Boxers and many other breeds, this can lead to breathing and respiratory problems. Boxers also face problems with a specific Cardiomyopathy that only Boxers can get that is usually fatal.