Extent of Inbreeding in Purebreds Revealed
I know certain breeds of dogs are predisposed to having certain conditions but I had never given it much thought as to why.
A new study from researchers at Imperial College London shows the extent of inbreeding in purebred dogs and how this reduces their genetic variation.
Inbreeding in pedigree dogs arises because certain dogs, prized for exhibiting the characteristics desirable for that breed, are used to father many litters of puppies. When dogs from these litters come to be mated, some will be paired with dogs having the same father from other litters. Over generations, more and more dogs across a particular pedigree are related to one another and the chances of relatives mating increase.
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.
Interesting stuff.
For those of you that get the BBC One, the researchers will discuss the study on “Pedigree Dogs Exposed” which airs on Tuesday 19 August 2008 at 21.00 BST.
This is exactly why most mixed-breed dogs are actually healthier and live longer with less genetic medical problems than purebred dogs. It’s a shame that the breeds we love are in such danger….. Where will they be in another 5 years? 10 years? 50 years?
I’ve been saying this for a long time. It’s why I have problems with places like the AKC, with their slogan of “For the good of the Purebred Dog,” or something like that. The only purebreds I’ve ever had were a couple of beagles when I was a kid, and my current oldest two dogs, which are purebred Poms. Other than that, all my dogs are mutts, and my Poms have far more health problems than the mutts.
What I ask is, why can’t we have a national kennel club for mutts?
“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″
Different breeds only came about through imbreeding. It is not a new thing. Neither sisters and brothers, nor mothers or fathers with offspring, should be bred, and responsible breeders will not breed such close relatives.
“Why can’t we have a national kennel club for mutts?”
Think about all of the mutts that are killed each year because people do not spay and neuter… if their was a national kennel club for mutts, people would have more excuses for not spaying their dogs and more dogs would be euthanized. Under no condition should a mixed breed dog be bred (nor a purebred dog without the proper pedigree) too many dogs have to die each year.
Closed stud books + Dictator-Like AKC = Unhealthy Breeds
“Different breeds only came about through imbreeding. It is not a new thing.”
I would disagree. It’s not “inbreeding” that creates new breeds; rather it’s “interbreeding” that new breeds come from. Only though an interaction of the genes from wholly different parents do evolutionary improvements happen. It does not matter whether a purebred is bred to it’s mother or some dog from across the country, you can still trace their genes back to a common ancestor, probably not more than a hundred or more years ago. In many cases, probably even more recent. The problem is the defective genes from that ancestor have been passed down to all it’s current generation because no new blood is ever introduced.
“Under no condition should a mixed breed dog be bred…”
By that notion, then you are saying that all natural evolution in dogs should be halted, allowing only those breeds that are considered “purebred” to continue to exist. That would mean that no new blood will ever again be introduced to those bloodlines and probably within the next 300 years or so, domestic dogs would be extinct, or at least so burdened by health problems that they would only live a year or two. Interbreeding is the natural way of selecting the superior traits of the current generation and passing them on to the next.
OkinaJuan — that’s just offensive — granted I don’t look like the anorexic model (which is the “standard look” for humans by the way) but we’re not all unkempt trailer trash thank you.
I own all purebred dogs. Responsbile breeders screen for health problems in their breed and minimize them. We now have genetic markers to help.
A lot of the problems come from backyard breeders and puppy mills where unhealthy dogs are being bred to make a quick buck. So many people go to a pet store and pay an unreasonably high amount for an unhealthy puppy. These people then say they resuced the pup from the pet store. The biggest problem is uneducated buyers who want a puppy or dog NOW. They do no research and go to a pet shop or buy a puppy off of the internet. Well, I say shame on you. Whether you want a purebred or an all american you should do your research and take your time to find the best possible puppy or dog that fits your lifestyle. I’ve seen plenty of mutts with hip dysplasia and epilepsy.
I’m also tired of purebred breeders and fanciers being constantly put down. Dedicated breeders work very hard to produce healthy happy dogs. They give up their lives for their chosen breeds and often they rescue puppy mill dogs because they love their breed. They don’t make money. It costs a lot of money to have health clearences done.
Let’s put the blame where it belongs. It belongs with puppy mills and designer dog breeders who mix 2 breeds together and try to call them purebreds. But, most of all it belongs to the buyer who needs instant gratification and can’t wait for that well bred puppy, or can’t be bothered to do the necessary research and find a reputable breeder.
If the lines involved lack negative recessives, what’s the big deal with inbreeding? Just look at golden hamsters. Mitochondrial DNA analysis has confirmed that all domestic golden hamsters are descended from one female. All my dogs come from responsible breeders who do genetic screening.
“If the lines involved lack negative recessives, what’s the big deal with inbreeding?”
Haika, there are no lines that lack negative recessives. This is a proven fact and that is the point.
When lines of mice are inbred to get rid of negative recessives the scientists carefully doing so lose 90% of the lines. Is that really how we want to do when breeding dogs – lose 90% of the pups in order to establish some odd idea of purity and perfection?
Then there is the whole issue of the immune system and the major histocompatibility complex, a cluster of genes essential to the immune system that, by early studies, work best when diverse.
It is NOT just BYBs and mills contributing to the poor health of purebred dogs. It IS the closed registry system and the rewarding of ribbons to dogs of best “type” when that type is predominantly defined by outward appearance.
I support breeding and breeders, but not necessarily closed stud books which have only been at play the last 50 or so years. Prior to that there were ways to bring new genes into a breed. We are finding out that was important. Some purebred breeders are doing a magnificent job and are very knowledgeable. Many, many others are not.
In the Cavalier breed only 2% of registered pups are born from breeders fully health testing, and many of those who don’t are involved in the ring. I imagine this would compare in other breeds.
There is room for improvement in the clubs, and chances to critically examine systems and processes that may help the future breeding of our breeds should be welcomed.
Resorting to “us and them” mentality solves nothing. As I have read many of the queries made by the producer of this documentary I believe the film will be fair and offer insight and suggestions.
We’ll have to wait to see. I’ll reserve judgement on the film until I see it, but I do believe it is stirring up important conversation.
Sissee
The reason we are seeing a higher concentration of homozygous recessive mutations or conditions in purebreds is because breeders are no longer properly doing their jobs.
Pedigrees were supposed to be kept so that specimens could be carefully bred in order to reduce the amount of defects and mutations in the breeding population.
Some breeders do an excellent job; however, there are those that see opportunities to walk away with a bag full of money. Careful breeding to the breed standards seems to have taken a backseat.
The majority of breeders are just in it for the money.
sissee:
Golden hamsters were not bred to remove negative recessives. It’s actually possible to breed two critters together who do not carry lethal/negative recessives. That’s the point.
I’d like to read the peer-reviewed paper you refer to when mentioning that all dog lines carry negative recessives. I have ready access to MedLine and all medical/biological scientific literature. Thanks!
Time to educate buyers. I would never consider a puppy if I couldn’t get genetic screening data on ancestors going back at least 5 generations. This information is commonly available in my breed and data is available in a researchable data base. When I joined my breed club (Siberians), I signed a code of ethics that required that I do genetic screening on my dogs if I bred. Most of us do genetic screening on all stock just to provide the type of useful information necessary when making responsible breeding choices. But then I am involved in a relatively healthy breed (also one of the most ancient breeds). When I was involved with rough collies, the situation was similar. So, no….sounds like the situation in your breed isn’t ’standard procedure’.
One of our best dogs is a mutt. However, there is a HUGH difference in purebred breeders. I suspect that many have fallen to the almighty dollar. Thus, creating genetic problems and a bad name for the rest. There are responsible purebred breeders out there. You must be a diligent and responsible buyer as well.
I’m surprise that during these last years there have been a variety of new breeds in which we never had thought that those would be in a better conditions, stronger and healthier than the rest. I do like these new mixture, of course who doesn’t like weird dogs?
Ninie
Outsourcing In Call Center
This is why everyone ought to opt to adopt instead of supporting a breeder of ANY kind. Why buy when you can save a life?
Come on people…get a clue!
The answer is to encourage RESPONSIBLE breeders who breed for the health of the dog breeds and the standard, but more for health than matching the standard.
Also, inbreeding, the breeding of closely related animals, should be DIScouraged greatly.
cookiemiller.tripod.com
I’m a future breeding doing research. Thank you for posting this article.
“This is why everyone ought to opt to adopt instead of supporting a breeder of ANY kind. Why buy when you can save a life?
Come on people…get a clue!”
Without reputable breeders, the breeds would fall apart even more. We should discourage bad breeders ONLY.
I strongly advocate adopting, but I also strongly advocate reputable breeders.
I’ve adopted, and I’ve bought. Personally, I’ll keep on adopting AND buying dogs, thank you.
Sorry, Lisa, but when I see your posts, they make me want to get all the rest of my dogs from breeders.
Why buy when you can save a life? That is very reminiscent of PETA’s, if you buy a dog from a breeder and shelter dog must die.
Lisa, I don’t want a bully mix, or a large shaggy dog, or a small dog – that’s what’s generally available at the shelter. Those are all perfectly lovely dogs, but I love my Shepherds. And, I’m not overly fond of GSDs of a certain type, I prefer the European style dogs. I’m sort of picky and since I only get a fixed number of dogs in my life, that’s what I want whether I buy it, adopt it or rescue it.
I’d like to read the peer-reviewed paper you refer to when mentioning that all dog lines carry negative recessives
Here’s one:
http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pubmed&pubmedid=17966340
(…)
. Heterozygosity is an important occurrence for species’ fortitude and survival (1). The Hardy-Weinberg Principle describes how a natural balance, in most species, maintains a high degree of genotypic heterozygosity in order to preserve genetic fitness and, hence, species’ health (2,4,18,19). High rates of homozygosity can occur in nature due to “bottleneck situations,” such as a limited gene pool in island populations, but in canines, homozygosity is deliberately accomplished by people trying to achieve specific breed standards. Many desired breed traits are recessive, rather than dominant, and require that both copies of the inherited alleles be the same for the trait to be expressed phenotypically. Individuals selected for consistent expression of alleles specific to desired physical traits results in offspring that are homozygous.
Breed purity and genotypic homozygosity is harmful to canine health because it requires inbreeding and results in an abnormally high occurrence of inherited diseases. Unfortunately, when breeders selectively “double up” on desired traits for physical conformation, they also double up on genes that can result in decreased fitness and increased disease. All individuals carry deleterious genes, but they are usually inherited in a heterozygous state and, therefore, not expressed. Because these genes are ordinarily recessive, there is no detrimental impact on health (4). In effect, a heterozygous state frequently confers a selective advantage by creating a larger store of genetic variability. Deleterious alleles are still present in heterozygous populations; however, when infrequent homozygosity of these genes occurs naturally, the individuals are eliminated through natural selection, due to their inferior fitness. The existence of deleterious alleles in a population, therefore, does not affect a species’ overall fitness (3).
(….)
Thank you. I have to say that I feel this is an overgeneralized approach to canine genetic inheritance and appears to be based on broad assumptions with little direct data. I’m curious why the ancient purebreds aren’t discussed here, i.e. those breeds that go back 20,000 or more years. Although I do need to read the entire paper, it appears that all purebreds are lumped into one ‘dangerous breeding practices’ category and I do not think that is useful. I’d LOVE to read the peer-review comments on this paper. However, I am unfamiliar with how robust the review process IS for this journal. It’s outside my direct field and I have not published in this journal.
I read a great book about this recently: Dogs: A Startling New Understanding of Canine Origin, Behavior & Evolution by Raymond & Lorna Coppinger. It also debunks the popular legend that wolves are the ancestors of dogs.
I wrote a paper about dog breeding, and here’s the paragraph about dog breeding:
Sorry, the above comment came out wrong. Blech. Let me try the quote again (because that wasn’t it):
Modern-day breeding began in the early twentieth century. Breed standards were written and studbooks were closed “for purity’s sake.” (Budiansky 220). The idea is almost to change each breed into a separate species. However, closing studbooks is much like dropping the guillotine on a group of dogs. Inbreeding has to occur if the breed is to survive to the next generation. Depending on the number of founding dogs, inbreeding may be delayed for a few years. “If I created a breed of dogs in 1900 (that is, closed the stud book) with five hundred males, [by 2000] that breed would have been inbreeding for eighty-five years.” This is a recipe for genetic diseases and general poor health (Coppinger et al. 316). Every recognized breed with a closed studbook has a list of diseases and health problems that go with it. “It is all rather like reading an account of the royal families of Europe after everyone had spent a few hundred years marrying their first cousins” (Budiansky 216). Even worse, most breeders believe that genetic testing can help cull diseased dogs from the population. “DNA tests now exist for many single-gene diseases, and the near future will see an avalanche of such tests, and perhaps some for polygenic diseases” (Coile, Ph.D. 20). Removing dogs from the gene pool only increases inbreeding (Coppinger et al. 316).
Katie:
I’[m trying to understand what you are suggesting. At appears that you do not support genetic screening since the results can be used to remove a dog from the gene pool and hence reduce the gene pool. Wouldn’t retention and breeding of the dogs that either carry the trait or exhibit the trait lead to an INCREASE in the disease statistics? I’m not sure what your goal is here.
I think it’s very important to consider the relative genetic health of breeds that have been around for many many thousands of years (the ancient breeds), e.g. saluki, samoyed, Siberian husky, basenji, etc.
I also disagree with the popular statement: “We need to support good, responsible breeders!” Breeding is not ever done for the health of the dogs; it’s done to appeal to different people’s visual tastes. Inbreeding must occur with every breeding kennel, even with the so-called ‘responsible’ breeders. When it gets right down to it, purebreeding really started in the Victorian Era as a visible indicator of social status, and that’s still what it is.
I’m disagreeing with that. Why? I’m a breeder-in-training and the one and only reason I even want to breed is to keep the dog breeds (in my case, Collies and Shelties) healthy.
I have my website:
cookiemiller.tripod.com
Line-breeding, a form of inbreeding, can be very helpful, but should ONLY be done bu someone who is knowledgeable in genetics and who is experience in breeding dogs.
IMO, the way to stop this train wreck, is to discourage irresponsible breeders with all of our capacity and to encourage responsible ones who do the proper health testing, evaluating and what the dog was bred for.
Disagree with that as much as you wish, that’s my personal opinion and I’m open-minded, but slow to change my opinions.
P.S.
Breeding is not ever done for the health of the dogs; it’s done to appeal to different people’s visual tastes.
No, it’s done partly and indirectly to supply people with dogs that fit their lifestyle. Different breeds fit different people. No one breed works for everyone. I’m always telling people looking for advice on what breed to choose to never choose a dog based on looks, because that can lead to disaster. For example, say that I chose a Border Collie because I like their looks but after buying one I found that I couldn’t handle their shy high energy, exercise needs, and/or grooming needs.
Even worse, most breeders believe that genetic testing can help cull diseased dogs from the population. “DNA tests now exist for many single-gene diseases, and the near future will see an avalanche of such tests, and perhaps some for polygenic diseases” (Coile, Ph.D. 20). Removing dogs from the gene pool only increases inbreeding (Coppinger et al. 316).
Genetic testing is important. However, it is true that “Removing dogs from the gene pool only increases inbreeding “. That is why some breeds may have to have people breed them even if they don’t pass certain genetic tests. I think that there is a balance. I think that in SOME cases, inbreeding can be helpful if you really know what you are doing. Linebreeding, as I stated earlier, is helpful and IMO better than outright inbreeding.
P.P.P.S.
I need to start reviewing my posts so I won’t have to keep making different posts.
Earlier I said:
“No, it’s done partly and indirectly to supply people with dogs that fit their lifestyle. Different breeds fit different people. No one breed works for everyone. I’m always telling people looking for advice on what breed to choose to never choose a dog based on looks, because that can lead to disaster. For example, say that I chose a Border Collie because I like their looks but after buying one I found that I couldn’t handle their shy high energy, exercise needs, and/or grooming needs.”
I just wanted to add that the other part of breeding IS to keep the breeds healthy.
Also, the way to keep the dog breeds where people can find the best breed for them is to try to keep the dogs according to standard as possible. The standard is NOT perfect, but it is something to breed to. Without a standard, the breed’s looks would start to vary more and more and after a while it would be hard to identify one breed from another, not to mention it would be much harder for people to find the best breed for them.
That’s all I have to say for now.
P.P.P.P.S.
Arg, another post from me because I forgot to mention something.
There are very few truly reputable breeders in this day and age.