We all know that inbreeding - mating close relatives together - is obviously a very dangerous game. Nothing new here. But Professor David Balding used the Kennel Club's database of pedigees to analyse just how closely related dogs in several breeds actually are.
The researchers' analysis showed that, for example, Boxer dogs were so closely related to one another and had such little genetic variation between them that genetically, 20,000 dogs looked like a population of about 70. In the Rough Collie breed, 12,000 dogs looked in genetic terms like a population of about 50.
Professor Balding was quoted as saying: "The idea that inbreeding causes health problems in particular dog breeds is not a new one, but we believe ours is the first scientific study to explore this issue and analyse the extent of inbreeding in a systematic way, across many breeds. We hope that following our work, dog breeders will make it a high priority to increase the genetic diversity within different breeds. Otherwise, we will see growing numbers of dogs born with serious genetically inherited health problems."
The report says: "Such small effective population sizes mean that the chances of a dog breeding with a close relative, resulting in birth defects and genetically inherited health problems, are high. The researchers argue that those involved in breeding dogs should encourage breeding from a larger pool of potential mates in order to create greater genetic variation and lessen dogs' chances of inheriting genetic disorders. They suggest measures such as limiting how many times a popular dog can father litters; encouraging mating across national and continental boundaries; and relaxing breed rules to permit breeding outside the pedigree."
Surely the KC will find it very hard to allege bias if the whole scientific community are saying "panic".
But the KC is trying to convince themselves that everything is still okay - they've got it all under control. That the only people who say otherwise are very bad biased people with issues.
I have to say some of the behaviour on the dog show forums where the BBC1 documentary has been discussed has been really quite shocking. Some of the pack are obviously very scared of this programme and some of them are getting nasty, calling the producers of this documentary "evil" just for asking them difficult questions about health issues in the usually safe enclave of their own dog shows and forums.
I know there are free-thinking breeders who question the status quo and worry about the future of their breeds who will watch the programme with an open mind and a heavy heart. Hopefully they will be brave in the coming days and their voices will be heard, too - and not just these short-sighted luddites who are an embarrassment to the pedigree dog world.
The brilliant blogger Terrierman has already had a good read of the report and here is his summary....
- The study is based on a 10-breed sample of 2.1 million dogs in the Kennel Club's electronic pedigree data base. The Kennel Club's database contained records of a total of 5.7 million dogs from 207 breeds as of the end of 2006. The Kennel Club's electronic data base was begun in 1970.
- This is the first systematic attempt to study Kennel Club population structure using The Kennel Club's own pedigree database.
- The 10 breeds examined were: the Rough Collie, the Golden Retriever, the Boxer, the English Bulldog, the Chow Chow, the Greyhound, the German Shepherd Dog, the Labrador Retriever, the English Springer Spaniel, and the Akita Inu.
- The researchers note that inbreeding condenses and exacerbates genetic disorders with a population:
"Dog breeds are required to conform to a breed standard, the pursuit of which often involves intensive inbreeding .... This has adverse consequences in terms of loss of genetic variability and high prevalence of recessive genetic disorders. These features make purebred dogs attractive for the study of genetic disorders, but raise concerns about canine welfare."
- The researchers note that many dog breeds are associated with specific genetic disorders that have been magnified by inbreeding:
"Many diseases affecting dogs have high prevalence in one or a few breeds, such as Addison’s disease, common in Portuguese Water Dogs (Chase et al., 2006), interstitial lung disease in West Highland White terriers (Norris et al., 2005), and dermoid sinus in Ridgeback dogs (Salmon Hillbertz et al., 2007)."
- The authors found disturbingly high levels of inbreeding within most Kennel Club breeds they looked at:
"We find extremely inbred dogs in each breed except the Greyhound, and estimate an inbreeding effective population size between 40 and 80 for all but two breeds. For all but three breeds, more than 90% of unique genetic variants are lost over six generations, indicating a dramatic effect of reeding patterns on genetic diversity."
- The number of generations studied ranged by breed from 5.9 in Greyhounds to 9.0 in the German Shepherds, with an average over the ten breeds of 8.0 generations of dogs analyzed.
- Popular sires are part of the problem, but not all of the problem.
"Popular sires (defined here as > 100 recorded offspring) are evident in all breeds except Greyhound. Golden Retrievers have the largest proportion of popular sires (10%), and conversely the lowest proportion (5%) of male dogs that are sires. . . . Highly-prolific dams (> 40 offspring) are concentrated in three breeds: German Shepherd, Golden Retriever and Labrador Retriever. Most dams have just one litter recorded."
- A closed registry system is the core of the problem.
"Dog registration rules have only been rigidly enforced for about 50 years, prior to that occasional outcrossing was still possible."
- The Kennel Club needs to change the way it does business.
"We have found that the loss of genetic diversity is very high, with many breeds losing over 90% of singleton variants in just six generations. On the basis of these results, we concur with Leroy et al. (2006) that remedial action to maintain or increase genetic diversity should now be a high priority in the interests of the health of purebred dogs. Possible remedial action includes limits on the use of popular sires, encouragement of matings across national and continental boundaries, and even the relaxation of breed rules to permit controlled outcrossing."