While purebred dogs may be the best in show, are they the worst in health?

With its soft and affectionate disposition, combined with silky fur and elegantly floppy ears, the Cavalier King Charles Spaniel is a popular breed, with families paying hundreds, sometimes thousands, of dollars per puppy. Unfortunately, it is almost certain that their pet will also have genetic disorders.

By the age of five, for example, half of all riders will develop mitral valve disease, a serious heart disease that leaves dogs susceptible to premature death. At the same age, up to 70 percent will suffer from canine syringomyelia, a debilitating neurological disorder in which the brain is too large for the skull, causing severe pain in the neck and shoulders, as well as damage to parts of the body. dog spinal cord. And while horsemen are a particularly obvious case of a problematic purebred, they are not alone. Today, most purebred dogs are at high risk for many hereditary diseases. Why did this happen and what can be done about it?

Consequences of reproduction
For nearly 4,000 years, people have been breeding dogs for certain traits, whether they are an ideal physique for chasing away parasites like badgers, or a temperament suited to companionship. But the large number of modern breeds – and the roots of their genetic problems – have emerged over the past two centuries, when dog shows became popular and people began to selectively breed animals to have specific physical characteristics. Over time the American Kennel Club (AKC) and other similar organizations have set standards defining what each strain should look like. To promote the desired appearance, breeders often look to line breeding, a type of inbreeding that mates with direct parents, such as grandmother and grandson. When a male dog wins many championships, for example, he is often bred on a large scale, a practice known as popular bull syndrome (pdf) – and his genes, healthy or not, then spread like wildfire throughout the breed. As a result, purebred dogs not only have an increased incidence of hereditary diseases, but also increased health problems due to their figure and body shapes, such as hip dysplasia in large breeds like the Shepherd. German and St. Bernard, and patellar dislocation or persistent dislocation. of the patella, in toy and miniature breeds.

How did we come to this situation? “Historically, a breeder’s primary concern was to produce dogs that resembled the breed standard,” explains James serpell, professor of ethics and animal welfare and director of Center for the Interaction between Animals and Society at the University of Pennsylvania School of Veterinary Medicine. “Even though they recognized health issues, the breeders were too motivated to produce what was perceived to be the most perfect breed.”

In the 1850s, for example, the bulldog look at more like today’s pit bull terrier – sturdy, energetic and athletic with a more elongated muzzle. But at the start of the 20th century, when dog shows became popular, the bulldog had acquired stocky, bandaged legs and a large head with a flattened muzzle. This altered figure makes it almost impossible for them to reproduce without help, and the facial changes cause severe breathing problems in a third of all bulldogs. Breeders frequently turn to artificial insemination because the bone structure of the female bulldog cannot support the weight of the male during mating. Most also cannot give birth naturally, as puppies’ heads are too large for the birth canal.

The large head and short legs are part of the written standard, so Serpell believes those standards would have forced the bulldog to disappear if the breeders did not rely on artificial insemination. “By essentially requiring the judges to select animals that meet the written standard, the club has, in a way, signed the bulldog’s death warrant,” said Serpell.

Despite the negative effects of controlled breeding, animal science experts emphasize the value of selection for consistency. “A breed standard is the model providing information about appearance and temperament and reflects the original function and purpose of the breed,” explains Milan hess, a Colorado vet who works with the AKC. When choosing a dog as a pet, consumers look to the breed standard for greater certainty. “They know what it will look like and how it will act,” says Thomas Famula, breeding specialist at the University of California, Davis.

Healthy choices
However, with the pursuit of consistency producing unforeseen flaws, whose fault is it? Although the AKC sets the breed standards, it is primarily a registration body and has little control over the selection process itself. Famula believes that dog breeders hold the highest responsibility as they make the decisions about which dogs to mate. “Ultimately, it’s the breeders who create the next generation of dogs,” says Famula. But researchers like Famula and Jerold bell, a geneticist at Tufts University Cummings School of Veterinary Medicine, notes that breeding practices are greatly influenced by buyers of puppies who Bell says are largely unaware of genetic issues. “The public is completely oblivious. They see a cute dog and are sold, ”says Bell. When purchasing a puppy, buyers may ask for medical tests and a family history of illnesses; but this rarely happens. “Although this is ultimately the responsibility of the breeders, if there is no pressure from the buyer, the system will not change,” he adds, noting that most Top 10 diseases that affect all dogs are controlled by unique genes which, once identified, are easily eliminated in the next generation.

Meanwhile, many organizations breeding dogs for police work or to help people with disabilities routinely use data registries to keep health information and make smart pairing decisions that reduce the prevalence of inherited diseases. The eye that sees, a guide dog school in Morristown, NJ, for example, uses genetic testing and maintains a database that tracks potential problems in all dogs. “We have a geneticist on staff who assesses each dog as a potential breeder, and we sometimes bring dogs from other guide schools to make sure our genetic makeup is not too small,” says Michelle Barlak, Senior Public Relations Associate at The Seeing. Eye.

Moving forward
It is possible to improve a breed and keep its characteristics, of course. Consider the Dalmatian. The Challenge: The genes responsible for the breed’s characteristic sought-after spot pattern also cause elevated levels of uric acid in the breed’s urine, predisposing them to the formation of urate crystals which frequently cause urinary blockages. Selection against uric acid, however, would result in a flawless Dalmatian. Now there is new hope from the work that began in 1973, when Robert Schaible, a geneticist at Indiana University School of Medicine, initiated the Dalmatian-English Pointer Backcross Project. He paired an AKC champion Dalmatian with an English pointer, a breed with normal uric acid levels and a Dalmatian-like disposition, then crossed a dog of that litter to another Dalmatian and so on. . In 2011, after 15 generations, the AKC authorized Dalmatians of this healthier pedigree, spots intact, to register.

Looking to the future of purebreds, Serpell stresses that the goal is not to get rid of them but rather to put animal health first. “I don’t think anyone wants races to go away,” Serpell says. “I don’t want the Bulldog to go extinct, I just want the Bulldog to be transformed again into an animal that is able to function properly and is in fairly good health.”

This article is provided by Scientific line, a project of the New York University Science, Health, and Environment Reporting Program.

Source link

Jeanetta J. Stewart

Leave a Reply

Your email address will not be published.