Breeding Discontentby Paula Kislak, DVM November 14, 2011
 While natural selection leads to hybrid vigor, selective dog breeding has lead to more than 300 documented heritable and congenital diseases. iStock Geneticists and archeologists have confirmed that domestic dogs (Canis lupus familiaris) all share a common ancestor: the gray wolf (Canis lupus). This was proven by comparing the DNA of many modern domestic dog breeds to that of wolves, coyotes, and jackals. Exactly when and where wolves were first domesticated is unsettled, bur recent research indicates that it may have been as long ago as 32,000 years. Some of their ancient history with humans can be gleaned from fossil records. The oldest domestic dog remains date back 14,000 years and the oldest known burial of a dog with a human dates back 12,000 years. Since then, dogs have been selectively bred for countless generations resulting in over 400 distinct canine breeds. They can have over a three hundred-fold weight difference, and they represent the most diverse mammalian species alive. The smallest known dog was a Yorkshire Terrier who weighed a quarter of a pound, while the largest, an English Mastiff, weighed in at 343 pounds. Humans and dogs formed a mutually beneficial relationship from the start. While humans supplied dogs with a reliable food source, they also benefited from dogs’ hunting abilities. And dogs' association with humans facilitated earlier and more frequent dog breeding, including those individuals in the gene pool who may not have reproduced at all in the wild due to low social standing in their pack. In 2004 the National Institutes of Health published findings that grouped modern domestic dog breeds according to their genetic similarities. Using 85 dog breeds and several wolves, researchers grouped breeds of dogs according to how genetically similar they are to the gray wolf. The oldest group of dog breeds—those most similar to their wolf ancestors—contains Asian breeds: the Shar-Pei, Shiba Inu, Akita, and Chow Chow. The second oldest group consists of the Basenji, an African breed. The third oldest group includes two Arctic breeds, Alaskan Malamutes and Siberian Huskies. Lastly, two Middle Eastern sight hounds make up the fourth group: Afghans and Salukis. Surprisingly, some breeds thought to be ancient, such as the Pharaoh Hound and Ibizan Hound, were revealed to have much more modern roots, probably due to human efforts to recreate ancient canine appearances. The other, newer breeds analyzed had less in common with the gray wolf, and each other, genetically than did those of the four ancient-rooted dog groups, sometimes referred to as “old-world dogs.” For most of our shared history, there were only a few distinct dog breeds and dogs were primarily bred for their utility. Only in the last few centuries, as humans began to understand and manipulate genetics, has there been an explosion in the number of "designer" breeds that now represent a majority of the modern breeds we know today.  Dr. Kislak with a photo of her late Greyhound, Jasper. Paula Kislak, DVM My interest in this topic was sparked when I became hopelessly smitten with Greyhounds. I fell in love with them in veterinary school and when I graduated, I left school with two of them. I was already aware of the origin of modern dogs and had an inkling about their inherent flaws, but I was feeling pretty clever that my chosen breed was a strong one—genetically engineered, to be sure—but designed to produce healthy, athletic dogs. My fantasy started unraveling rather quickly. It turns out that although the selective breeding of Greyhounds for athletic prowess spared them many common conditions that afflict large-breed dogs, like hip dysplasia, Greyhounds inherited a predisposition for other diseases, some lethal, with heartbreaking frequency. Because these gentle, graceful hounds were essentially disposable—they were either killed on the racetrack at any sign of illness, or killed routinely by three or four years of age—this genetic shift went largely undetected until the last decade when they began living out retirement in loving adoptive homes. I subsequently learned there is simply no way to artificially manipulate genetic codes without incurring tragic unintended consequences. The widespread and deliberate practice of inbreeding closely-related family members possessing exaggerated physical traits has created modern dog breeds, but it is also responsible for the 334 documented heritable and congenital diseases like hemophilia, epilepsy, heart disease, and many cancers (see the HSVMA Guide to Congenital and Heritable Disorders in Dogs for more detail). And scientists in Sweden who studied over 13,000 dogs from 31 breeds have found strong evidence that breeding for appearance has led to a decline in canine intelligence as well. Selective dog breeding is a powerful demonstration of evolution, but instead of survival of the fittest, it is survival of the cutest, often defined as those who garner the most dog show awards and command the highest breeding fees. These are the ones who are allowed to survive and reproduce. It became obvious to me how natural selection led to the robust hybrid vigor of mixed breed dogs and how inbreeding led too often to disease, disability and death of purebred dogs. Reflecting on these outcomes, some of my veterinary colleagues and I concluded that a disproportionately large amount of time in our practice careers has been spent mitigating the results of manipulative breeding. These points are highlighted in the Royal SPCA position statement on pedigree dogs:
The scale of resultant suffering is immense and the degradation of the canine species is a major consequence of breeding purebred dogs. When you add puppy mill abuses, the 3-4 million unwanted shelter animals killed each year in the United States, and the fact that an estimated 25-30% of the dogs in shelters are purebreds, the scope of the problem is staggering. So what can be done? Again, the Royal SPCA got it right with this aspirational position statement on pedigree dogs:
As veterinary professionals in the United States, we should also encourage breeders to adhere to strict and humane codes of conduct, including provisions for breed-specific rescue. This would go a long way toward defusing the demands of those who believe there should be a temporary moratorium on breeding until the backlog of dogs is cleared and until each breed club has the opportunity to develop a plan to produce happier, healthier animals. Among other things, we should counsel our clients on the virtues of adopting hybrid (mixed-breed) dogs and facilitate innovative and aggressive marketing of shelter animals. We should also support sterilization of every adopted animal that leaves any facility, programs to keep "at risk" dogs in homes, and legislative efforts such as differential licensing to promote responsible behavior and enactment of puppy mill restrictions. All stakeholders should be involved—veterinarians, breeders and kennel club associations, animal protection and breed rescue organizations, drug and pet supply companies, pet insurers, the pet food industry, and companion animal guardians. And moving forward, we should forge cooperative alliances and develop robust plans to improve canine health and welfare with all these parties.  Dr. Paula Kislak Dr. Kislak is president of the HSVMA Board of Directors and also serves on the Board of Directors for The Humane Society of the United States. She has worked with the San Diego Humane Society and the Humane Society of Greater Miami, as well as in private practice positions in California. She has been involved in Greyhound rescue since graduating from the University of Florida College of Veterinary Medicine in 1984 and currently serves as an advisor for Homestretch Greyhound Rescue and Adoption. |