Saturday, May 2, 2009

Are genes really lost forever with inbreeding?


Recently I blogged about how few studies actually look at inbreeding in dogs - see What do dogs have in common with fruit flies?

One study that does look at dogs, or at least their pedigrees (even if was mainly conducted from the perspective of finding a research model for investigating human genetic diseases) is:

Population Structure and Inbreeding From Pedigree Analysis of Purebred Dogs

Many refer to this paper as the "Imperial Study"

There is one particular finding of this pedigree analysis study that genetic diversity purists in dogs focus on exclusively, and that is: "For all but 3 breeds, >90% of unique genetic variants are lost over six generations, indicating a dramatic effect of breeding patterns on genetic diversity."

Typically after citing this finding the genetic diversity purists in dogs will dramatically emphasize that:

"Inbreeding results in genes being lost forever!"

Let's take a closer look at this prediction of doom and gloom ...

Dr. Jerrold Bell, DVM, a clinical associate professor of genetics in the department of clinical sciences at Tufts University has stated that: "Inbreeding or linebreeding does not cause the loss of genes from a breed gene pool. It occurs through selection; the use and non-use of offspring. If some breeders linebreed to certain dogs that they favor, and others linebreed to other dogs that they favor, then breed-wide genetic diversity is maintained" (Bell. 2001)

Closed purebred registries, by their very nature, are dealing with a finite number of genes descending from the founding stock that helped to develop the breed in the first place. There will be no new genes added to a purebred population unless the studbooks are opened and cross-breeding (crossing different breeds to produce a mixed breed) is permitted. There are those who will argue this is necessary or will become necessary - it's important to bear in mind that some of these individuals are determined to erradicate dog breeds.

The reasons given by those who advocate cross-breeding is that purebred dogs breeds are inbred populations that cannot sustain longterm. This line of thinking basically ignores the examples of long-sustained inbred populations that can be found in the wild.

Their logic follows from population genetics models based on observations of wild animal populations which are subject to natural selection and random breeding. Of course most dogs are not subject to natural selection (unless they get lost in the wild) and most purebred dogs are not subject to random breeding.

Wild species populations are structured in terms of age, gender, and geographical location. As such the wild animal population structure does not fit the structure of domesticated dog populations.

Domesticated dog populations are composed of various breeds, and each breed population is further subdivided dog into subgroups based on breeding purpose: show breeding, working breeding, one-time breeding, puppymill breeding, commercial breeding, back-yard breeding, etc. And there are various levels of expertise on the part of the breeders found within each subgroup. There are no equals here.

Comparing between the subgrouping and levels of expertise is like comparing apples and oranges.

Some other findings of interest coming out of the Population Structure and Inbreeding From Pedigree Analysis of Purebred Dogs study include:

(1) Around 20% of dogs have a recorded offspring.

This finding dramatically illustrates just how many dogs are removed from the genepools of purebred dogs through non-use. In a wild population, any individual that survives to sexual maturity, that is not otherwise prevented from mating, will more than likely produce offspring and subsequent offspring in the following mating seasons. This is certainly not the case for dogs.

(2) Most dams have just one litter recorded.

Clearly "popular dams" are not an issue in purebred breeds. The best recommendation coming out of the genetic diversity movement in dogs is to use more males in breeds rather than many dogs being bred to popular sires. We all know that doing so typically leads to a glut of half brothers and sisters with no where to go for the next generation. There is a need to maintain distinct lines and to try to prevent lines from dying out due to lack of popularity. These are all important to breeds.

(3) Specifically, we estimate from simulations the probability that an allele chosen at random from a founder would be represented by a copy in generation 6. We found through simulations that for a random-mating population with a large, constant size, this probability is close to 25%.

Even in a random-mating population, such as a mixed breed dog population or wild species population there is only a 25% probability that a randomly chosen allele will be maintained after six generations (that's an estimated 75% loss). Obviously, alleles can be potentially lost within closed purebred registries and within closely related lines (the study reported a 10% probability that a randomly chosen allele would be maintained over six generations over the period of 36 years), but it is not inevitable since breeders are not all making the same breeding decisions as Dr. Bell has pointed out. In addition the Population Structure and Inbreeding From Pedigree Analysis of Purebred Dogs revealed that inbreeding can actually be "advantageous through generating extra rare-allele homozygotes". Inbreeding is not bad, it's just a breeding method for achieving a particular goal (increasing homozygosity for desireable traits characteristic of various breeds ) versus outcrossing (increasing genetic diversity and more generic dogs )

(4) A low proportion of genetic diversity is retained under strong inbreeding or when reproductive success is highly variable across individuals.

Not only are purebred dogs not subject to natural selection as wild popluations are, on top of that we spay/neuter thousands, if not millions, of perfectly healthy purebred dogs every year. Human and wild populations are not subjected to that kind of reduction to the genepool. If a person or wild animal survives to sexual maturity there is a good chance he/she will reproduce, not so for dogs.

Just by virtue of being a closed population some genetic loss in going to be expected since not every healthy dog that reaches sexual maturity will produce offspring and some level of relatedness is assumed since the entire breed descends from the same founders of the breed. From this study it would appear that that > 90% of genetic variation can be lost over six generations in situations of related breedings/increasing COI, however even in random-mating populations there is an expected 75% loss of genetic variation predicted over six generations. These findings are not "bad", just different effects for differing population circumstances. Genetic loss is an inherent risk for any population and is directly affected by the use and non-use of offspring (Bell, 2001).

According to geneticist and dog breeder Dr. Malcolm B. Willis (2009):

All purebred breeds begin with a certain amount of inbreeding. Largely this is done to establish the type of animal the breeders are seeking and to obtain some degree of uniformity. However, some generations on, the inbreeding will be much less. I made a study of British Boxer champions which covered 276 dogs over the period 1935 - 1975, only 13 of which were inbred 20 percent or more. 140 were inbred less than one per cent and the average inbreeding value for the population was 4.2 per cent. Included in this population are the "Wardrobes" Boxers, a kennel which used inbreeding to a considerable extent and to great success, during the fifties and sixties.A similar study to the Boxer one was undertaken on American GSD champions in ten year periods from 1940 to 1980. The study comprised 2,478 dogs; the percent of animals scoring an F value in excess of 20 was 2.9, 58 percent scored 5 or lower and 23 percent between five and ten. These are not indicative of high levels of "incest" breeding. The average in breeding for these American dogs is 5.3 per cent, which is less than first cousin mating.The consequences of inbreeding are varied because many defects are autosomal traits. One consequence of inbreeding could be an increase in abnormalities but this only applies if the population under study carries the defects. Inbreeding brings defects to the surface but does not create them.What can occur is inbreeding depression which leads to a reduction in fertility, a decrease in litter size, and an increase in mortality. However, inbreeding depression is not inevitable and over a period of time, numerically large breeds can show no adverse effects. In a study undertaken in 1908 on 29 litters of Bloodhounds, Heape showed a mean litter size of 10.06. I have recently undertaken a similar study on a similar number of litters in Bloodhounds and found the litter size to be a half a puppy less, which indicates that in a century of breeding, virtually there are no adverse effects on litter size.My own study of 3,331 GSD litters born in Germany in 1935 showed a litter size of 7.29. A German study (Winzenburger 1936) gave an average of 7.15 in 22,281 litters. Similarly my study in 1981 on 444 British litters gave a litter mean of 7.76. Humphrey and Warner in 1934, in a study of 104 litters of American dogs gave a litter size of 7.63.These all indicate minimum change in litter size over a long period of time. Professor Lush (Iowa State) in his classic book, "Animal Breeding Plans" (1945) argued that, "more opportunities for breed progress are lost by not inbreeding when inbreeding would be adviseable than are lost by too much inbreeding."This is not an invitation to inbreed willy-nilly but it certainly suggests that greater use can be made of it than is often done. Inbreeding has its biggest effect upon low heritability traits and much less of an effect on highly heritable characteristics; it may thus have minimal effect upon conformation (Willis, 2009).

Some people are ignoring or dismissing Willis' findings and focusing on the results of the Population Structure and Inbreeding From Pedigree Analysis of Purebred Dogs study to point fingers at show breeders and the "damage" they are doing to purebred dogs.

It's important to observe that no where in the paper is reference made to the type of breeding that the analyzed pedigrees came from.

And in fact the data can be broken into COI ranges that represent inbreeding (sibling to sibling, parent to offspring), linebreeding (presumably with occassional outcrossing), and outcrossing (within the breed to unrelated families). Here are the figures for the 13 breeds looked at in (across the entire pedigree database from 1970 to 2006).


Akita Inu:

COI >= 0.25 : 1.4%0.125 <= COI <> COI >= 0.125 : 10.2%0.0625 <= COI <> COI >= 0.0625 : 20.1%

  • Percentage Inbred (first-degree): COI greater than .25 = 1.4%
  • Percentage Linebred: COI greater than .0625 and less than .25 = 29.4%
  • Percentage Outcrossed: COI .0625 or less = 20.1 %

Boxer:

COI >= 0.25 : 1.6%0.125 <= COI <> COI >= 0.125 : 10.7%0.0625 <= COI <> COI >= 0.0625 : 20.1%
  • Percentage Inbred(first-degree): COI greater than .25 = 1.6%
  • Percentage Linebred: COI greater than .0625 and less than .25 = 30.2%
  • Percentage Outcrossed: COI .0625 or less = 20.1 %

Bulldog:

COI >= 0.25 : 0.7%0.125 <= COI <> COI >= 0.125 : 10.4%0.0625 <= COI <> COI >= 0.0625 : 23.1%

  • Percentage Inbred(first-degree): COI greater than .25 = 0.7%
  • Percentage Linebred: COI greater than .0625 and less than .25 = 32.8%
  • Percentage Outcrossed: COI .0625 or less = 23.1 %
Chow:

COI >= 0.25 : 0.8%0.125 <= COI <> COI >= 0.125 : 7.6%0.0625 <= COI <> COI >= 0.0625 : 16.2%
  • Percentage Inbred (first-degree): COI greater than .25 = 0.8%
  • Percentage Linebred: COI greater than .0625 and less than .25 = 23.1%
  • Percentage Outcrossed: COI .0625 or less = 20.1 %
Collie:

COI >= 0.25 : 1.6%0.125 <= COI <> COI >= 0.125 : 11.5%0.0625 <= COI <> COI >= 0.0625 : 20.4%
  • Percentage Inbred (first-degree): COI greater than .25 = 1.6%
  • Percentage Linebred: COI greater than .0625 and less than .25 = 30.3%
  • Percentage Outcrossed: COI .0625 or less = 20.4 %
Golden Retriever:

COI >= 0.25 : 0.6%0.125 <= COI <> COI >= 0.125 : 3.8%0.0625 <= COI <> COI >= 0.0625 : 11.4%
  • Percentage Inbred (first-degree): COI greater than .25 = 0.6%
  • Percentage Linebred: COI greater than .0625 and less than .25 = 14.6%
  • Percentage Outcrossed: COI .0625 or less = 11.4 %

Greyhound:

COI >= 0.25 : 1.7%0.125 <= COI <> COI >= 0.125 : 14.4%0.0625 <= COI <> COI >= 0.0625 : 24.8%

  • Percentage Inbred (first-degree): COI greater than .25 = 1.7%
  • Percentage Linebred: COI greater than .0625 and less than .25 = 37.6%
  • Percentage Outcrossed: COI .0625 or less = 11.4 %
German Shepherd:

COI >= 0.25 : 0.9%0.125 <= COI <> COI >= 0.125 : 4.5%0.0625 <= COI <> COI >= 0.0625 : 9.2%
  • Percentage Inbred (first-degree): COI greater than .25 = 0.9%
  • Percentage Linebred: COI greater than .0625 and less than .25 = 12.8%
  • Percentage Outcrossed: COI .0625 or less = 9.2%
Labrador Retriever:

COI >= 0.25 : 0.5%0.125 <= COI <> COI >= 0.125 : 2.4%0.0625 <= COI <> COI >= 0.0625 : 7.2%
  • Percentage Inbred (first-degree): COI greater than .25 = 0.5%
  • Percentage Linebred: COI greater than .0625 and less than .25 = 9.1%
  • Percentage Outcrossed: COI .0625 or less = 7.2 %
English Springer Spaniel:

COI >= 0.25 : 0.5%0.125 <= COI <> COI >= 0.125 : 3.1%0.0625 <= COI <> COI >= 0.0625 : 8.9%
  • Percentage Inbred (first-degree): COI greater than .25 = 0.5%
  • Percentage Linebred: COI greater than .0625 and less than .25 = 11.6%
  • Percentage Outcrossed: COI .0625 or less = 8.9%

Cavalier King Charles Spaniel:
COI >= 0.25 : 0.8%0.125 <= COI <> COI >= 0.125 : 5.6%0.0625 <= COI <> COI >= 0.0625 : 13.3%
  • Percentage Inbred (first-degree): COI greater than .25 = 0.8%
  • Percentage Linebred: COI greater than .0625 and less than .25 = 18.1%
  • Percentage Outcrossed: COI .0625 or less = 13.3%
Flat-Coated Retriever:

COI >= 0.25 : 0.5%0.125 <= COI <> COI >= 0.125 : 4.1%0.0625 <= COI <> COI >= 0.0625 : 14.8%
  • Percentage Inbred (first-degree): COI greater than .25 = 0.5%
  • Percentage Linebred: COI greater than .0625 and less than .25 = 18.4%
  • Percentage Outcrossed: COI .0625 or less = 14.8%
This set of data conclusively reveals that only about about 1 per cent of KC registered dogs has a COI of 25 per cent or greater (sibling to sibling, parent to offspring), and that the majority of each of the examined breeds fell in the two broad COI ranges associated with linebreeding/outcrossing and outcrossing breeding methods.

This data DOES NOT indicate the type of breeding of the breeds examined. That is, there is no way of knowing from the data if the analyzed pedigrees represented breeding for show/pet dogs, working/pet dogs, for profit pet breeding (one-time breeding, commercial breeding, backyard breeding), or outright accidental matings (which likely accounts for many of the 1% of > .25 inbred pedigrees).

It's also important to keep in mind that the Population Structure and Inbreeding From Pedigree Analysis of Purebred Dogs study analyzed KC registrations and the UK was until recently under restrictive quarantine regulations that curtailed the free flow of genetic material from other countries. Plenty of UK dogs have been exported internationally for decades, but the reverse was not true. This means that the levels of COI's found in this particular study may not be reflective of breed populations outside of the UK.

An e-mail from one of the Population Structure and Inbreeding From Pedigree Analysis of Purebred Dogs study authors:

Hello dog lovers,

I'm one of the authors of this article and would like to clarify that the Kennel Club gave us access to their registration database to assist us in planning studies of canine genetic diseases, with a view to both to help dogs and to help us understand similar diseases in humans (I am in a medical faculty, and am not really a dog person: small, cityapartment not suitable for dogs). It was only later that the idea came up of publishing a paper describing the pedigrees - including reporting inbreeding coefficients and effective population sizes. Jeff Sampson,the Genetics Co-ordinator of the KC, was very helpful in answering our queries and was keen for this information to get into the public domain. How or if Jeff disseminated our results within the KC I do not know, butI think that Caroline Kisko didn't know about it and got the wrong publication date because Imperial College put a story about our paper on its website just before the BBC TV programme, and it seems that Caroline assumed that this coincided with publication of the paper (she may have read a pre-publication version and not known the publication date). Whatever criticism the KC may deserve, I think it also deserves some credit for its co-operation with our research that had no immediate payback to them. For those of you interested in some of our results, but not inclined to read through a longish scientific paper, I have put on my website a poster that I presented at the Dog & Cat Genetics meeting in St Malolast May. You'll need to zoom in to each box to read it. Most of the results are from the paper, but there are some extra results that we did later on variance-effective population sizes. Surprisingly, there was almost no interest from the dog genetics people at the conference, norwas there much discussion there of inbreeding and its implications for canine health (I also suspect that the KC thought that our results wouldn't attract much attention). After all, that there is inbreeding in purebred dogs is not news. But Jemima and others found the results to be shocking, I guess because we have put numbers on it systematically over many breeds. For example we found that several major dog breeds inthe UK have the genetic variation equivalent to a population size of only about 50, often regarded as a threshold for a wild species to be regarded as seriously endangered. We also found that for many breeds,any one gene in a dog 6 generations ago has less than 10% chance of surviving until today, compared with a 25% chance in a random-mating population.

I hope this is of interest to some of you,

David Balding


Are genes really lost forever with inbreeding?

A purebred dog can only inherit the genes that it's parents contribute, so this may be true for a particular dog, but for the entire species of dogs? Of course not!

Purebred dogs by their very nature are homozygous for many gene pairs. That is what defines the breed. That is how the various characteristics of breeds were developed and how they are preserved. But dog species is composed of many breeds (with many unique different genes being maintained) as well as the mixed breed population. If a gene matters and is not to be found in a breed (and the Dalmatian is the only breed that comes to mind), it's only a matter of breeding outside the breed if a breed is actually in peril, and there is no other alternative. But after 100 years most breeds are sustaining or increasing in population size. For most breeds careful breeding and the use of available health tests will help breeders to produce healthy dogs. Lack of breed popularity is far more predictive of extinction than level of COI!!

That which can be found is never lost.

When making comparisons with wild animals (as David Balding did above) it's important to remember that a "the genetic variation equivalent to a population size of only about 50, often regarded as a threshold for a wild species to be regarded as seriously endangered" is hardly applicable to purebred dog breeds and the species of dogs as a whole.

A population size/genetic variation equivalent of 50 in a wild animal is cause for concern because that represents the species as a whole. A breed with the genetic variation equivalent to a population size of only about 50, is but one small piece of the species as a whole.

Dogs as a species are not in danger, in fact they are one of the most populace and successful species on the planet.

The problem is that some people are mistakenly viewing breed populations as species populations, which they clearly are not, and then erroneously drawing some rather dire conclusions for breeds.

Yes, purebred dogs have been developed out of inbreeding methods, and are being maintained with linebreeding and outcrossing methods. That's the nature of purebred breeds. That's not bad, it's just the way it is.

Every pedigree study of purebred dogs will reveal high, middle, and low COI's just as the paper discussed above has. As David Balding stated above "that there is inbreeding in purebred dogs is not news". Inbreeding at various levels is part and parcel to being purebred, but this does not mean the dogs are all suffering from genetic diseases. There is no established "optimal" COI. COI's greater than .25 do not indicate unhealthy individuals (it depends on whether double sets of defective genes were inherited). And it follows that a low COI of .o625 is no guarantee of health, since again it all depends on whether defective genes were inherited from the parents.

It's important to be wary of reading more into results than a study was designed to show. It's clearly mistaken and overly simplistic to draw negative conclusions of the health of a breed based on level of COI alone. To do so is ignoring the positive improvements breeders can make through careful linebreeding, conscientious selection of breeding animals, and responsible use of available phenotypic and DNA health tests.

Even Dr. John Armstrong, who started the genetic diversity movement in dogs, recognized the limited meaning of low COI's:"I keep reminding people that a low inbreeding coefficient does not guarantee a healthy, fertile and long-lived dog. In addition to its inherent limitations, there are just too many other factors involved."

The bottom line is that any breeding scheme is going to result in some gene loss whether as a result of artificial selection by breeders or natural selection by Mother Nature in random-mating populations. Breeders select for preferred traits and Mother Nature for fitness traits that will maximize survival. Normally the most advantageous genes will be preserved or maintained in a population.

Theoretically, in dog breeds it would be possible to maintain a maximum of genetic diversity if a maximum number of each breed was maintained in the genepool and used. But how practical is this? It would require the cooperation of puppy buyers to allow their dogs to be used in breeding programs, more litters than currently are produced, a need for more breeders, and a drastic reduction in spaying/neutering practises. This approach certainly could have the desireable effect of maintaining a maximum of genetic diversity in breeds, but at what expense? Possibly an abundance of dogs with no owners and an increase in accidental matings. Obviously there is a need for some balance.

There is one canine diversity purist who is advocating what he calls an "outbred nucleus colony". An outbred nucleus colony can be viewed as a sort of genetic feedlot for breeders to use to reduce high COI dogs in one breeding. The colony would be composed of dogs with COI's less than .625. It presents with some interesting dilemmas with respect to who and how and where, but especially with respect to need.

Afterall, there are breed populations all over the world with which a breeder could immediately reduce a pedigree to a COI of 0% if so desired. There has not been that much crossover of international and domestic lines in most breeds (apparently the Standard Poodle is an exception). From time to time one hears of breeders who say they cannot find any unrelated dogs to breed to within a breed. This is taken by some to be proof positive that genetic diversity is at a critical level of collapse. The truth be known, unrelated dogs can easily be found within most breeds, but are not neccessarily of the type or quality that the breeder wants to use. There is a big difference between not being able to find the quality/type of dog one wants versus being able find an unrelated dog within a breed.


One final comment

I am sure someone will question genetic diversity in dogs with respect to the Major Histocompatibility Complex (MHC), in particular the potential dangers of MHC homozygosity and predicted reduction in disease survivability that could effect an entire population and lead to extinction. It is a legitimate concern but there appear to be exceptions to the prediction. Both the highly inbred Cheetah and the inbred wolves of Ise Royale have been exposed to various feline infectious diseases and parvovirus, respectively. While there were losses from these diseases, neither species/population were wiped out, and subsequent blood titres indicate an immune response in the survivors. A similar trend was seen when parvovirus was first introduced in dogs, and distemper before that.

MHC functioning is important, but there is no evidence that dogs are currently in trouble with respect to MHC functioning, nor is there an established optimal level of COI beyond which MHC functioning would be expected to be compromised. In fact the immune responses within inbred populations in nature would suggest there is quite a bit of leeway with respect to immunocompetence. I'll write more on this later.

7 comments:

Jemima/Black Retriever X Rescue said...

I'd recommend that anyone interested in understanding more about genetic diversity and the effects of inbreeding do their own research. There has been much cherry-picking here and the conclusions are misleading.

Rather impolitely, you have also crossposted from the Canine Genetics list posts/information without permission from the authors.

Blog for Show Dogs said...

Cherry-picking? Isn't that what the person who feeds information to Terrierman from the OrigCanGen list does? In fact don't you know her?

I wouldn't expect one-sided thinkers to recognize comprehensive content when they see it.

Also you may wish to check out the definitions for cross-posting. In fact I'll do it for you:

Cross-posting: the simultaneous sending of a message to multiple news or discussion groups There are no crossposts to be found here.

There is no cross-posting happening here.

Commenting on opinions posted on various public forums is not cross-posting.

rufflyspeaking said...

I am passionately committed to the idea and the future of the purebred dog and its fancy, but unfortunately you've got some numbers and consistency problems here.

The first one is pretty basic - COI is a very fluid thing. In purebred dogs, COI is how many registered names are repeated over a certain number of generations. A one-generation COI is always zero (there's only one dog). A two-generation COI is always zero (there are only two dogs, and they are not the same dog). The vast majority of three- and four-generation COIs are very, very low. An eight-generation analysis is going to show a much lower coefficient than a 12-generation analysis. And so on.

Saying that breed X "has" a COI of a certain amount means nothing unless you define the number of generations. The study you referenced uses eight, polling breeds to 1970. If the dogs in the 1970s were already all cousins, but they had different registered names, the analysis will make it look like each one is completely unrelated. The vast majority of breed contractures occurred during the mass starvations and slaughters around WWII; if you want a more accurate COI on a breed you've got to go back to that point.

Second, as you say, the world of purebred breeding is sharply divided between the carelessly bred dogs (representing an overwhelming majority of most of the popular breeds) and the show-bred or performance-bred purebreds.

So it's useless to generalize about the state of a breed by looking at the broad registration statistics. Of course they're going to show low COI; they reflect a whole bunch of breeders who wouldn't know a linebreeding if it bit them. You have to look at registration statistics of the FANCY, and those you just don't have. You really need to pretty much chuck every conclusion you've drawn by looking at the raw study numbers, because they do not reflect the state of the fancy.

Along these same lines, you cannot look at the whole-breed registration numbers to tell whether a breed is growing and thriving. Show breeders would never, and will never, access probably 95% of the registered dogs of the popular breeds. They have effectively created breeds-within-breeds, and those numbers are closer to the true picture of what's happening with COI in the fancy. In the vast majority of show dogs, the show-bred population goes from one generation to the next on the backs of a few hundred dogs a year, and on a shocking number of breeds it's a few tens of dogs. The picture gets even more bleak when you realize how many breeds stick within rigid "color families" and have splintered the show-bred population into two or three or four never-the-twain-shall-meet branches.

Breeders of these dogs have absolutely zero intention of accessing (or ability to access) new genetic material; year after year it will be just fifty or seventy dogs that carry on the breed, or just twenty or thirty dogs that carry on the color family. So even a few years of preferring a certain stud dog or his relatives can radically skew an entire breed. And since we tend to run toward the dog or dog line that is perceived to be the closest to the standard, the breed lurches from one genetic side to the other with rather alarming frequency. As a result, founding lines that don't have dogs that are conformationally excellent are selected against or completely abandoned. Good for the silhouette of the dogs; not so good if you need unrelated pedigrees to breed into because the stud line of the year turns out to carry heart problems.

You've also run into the major common-sense problem of differing definitions of success. The Willis Boxer citation is a perfect one. He says "Look at this kennel, that inbred like crazy and was VERY successful!" The problem is that he's talking about show ring success, not longevity. He's talking about litter size, not survival rates, not life expectancy, not disease resistance, not immune systems.

If you look at the longevity of the Boxer, it's in the toilet. Ditto the Golden, the Flatcoat, etc. We have breeds that routinely lose half of each litter because newborn vitality is so low. We have working breeds that lose half their teeth before they're five. We have breeds that frequently attack their own adrenal glands. These are fundamental quality of life and soundness issues that indicate a breed that is far from succeeding.

Heck, look at your own writing - at the beginning you say that maintaining a closed studbook and tightening gene pools ever further is a fine thing, not harmful at all, and then you say at the end "Well, we can always cross-breed if we need to!" Either it's harmful or it's not; you can't straddle the fence.

As show breeders, we DO have to have an answer to the questions of genetic diversity. Most of us don't even come close. Part of that responsibility is acknowledging the truth of the numbers, doing additional research to see where the statistics change when you're talking only about show-bred dogs, and looking problems in the face.

I think people need to stop freaking out about flat faces or short legs. They need to stop blaming breeders for looking at a standard. They need to acknowledge the frantic efforts of breeders when confronted with a sudden disease in the breed. Breeders should be able to be proud of the structure and the beauty and the consistency of our dogs and their talents. But breeders have a responsibility too. We should feel secure about the "looks" issues, which don't impact quality of life or longevity, but we also have to start admitting that a breed with an average longevity of six to eight years (when it should be 12-14) really IS in a crisis. No matter how many of them are being registered.

Whether that unsoundness is actually a result of high COI or not, whether the answer turns out to be cross-breeding or not, nobody knows. But that doesn't give anyone permission to say that those breeds are in great shape.

Similarly, if we're going to keep maintaining breeds-within-breeds that have incredibly small populations and we're going to hold on to our closed studbooks, we really DO need to treat our breeds like endangered species. We can't have our cake and eat it too.

Look, I honestly don't know if you're right or wrong. The problem is that you don't either. We don't have the right research. It may be that when we place responsible and repeated research pressure on our show-bred populations we'll find that COI means nothing. I rather doubt it, but it could happen. In that case, everybody in the fancy can say "inbreeding is a great thing" with accuracy. However, right now we do not have ANY good numbers, ANY solid foundation, for claiming that a) we don't inbreed, really, all that much (ha!), or b) inbreeding is just fine, let's all do it.

Blog for Show Dogs said...

Mostly everything I have written in this blog highlights the lack of decent research in this area. I opppose people cramming a wild population model down the throats of breeders when there are no conclusive studies to be used in support of such an approach and Willis has presented some contrary evidence with regard to litter size (over 100 years)- his studies seem to be the only ones that actually look for evidence of inbreeding depression in purebred dogs as opposed to extrapolating from studies of genetically altered fruit flies and inbred mouse colonies. The fact remains that we don't know one way or the other. I would like to see some back up to this statement: "If you look at the longevity of the Boxer, it's in the toilet. Ditto the Golden, the Flatcoat, etc. We have breeds that routinely lose half of each litter because newborn vitality is so low. We have working breeds that lose half their teeth before they're five. We have breeds that frequently attack their own adrenal glands." For a while there it was all the rage to use raspberry leaves for dogs in whelp, everyone on the dog-related lists were following suit, until months later breeders were reporting puppies being whelped too early and losing significant numbers of puppies. That's just one example of an external influence on litter vitality - these are not straight forward observations that can be blamed on COI, etc. And in addition, exactly where are these dogs that are dying young, losing their teeth (I thought working dogs were genetically superior (HA!), suffering from adrenal failure, and losing litters coming from? Show breeders or pet/commercial breeders? This is the problem, no one ever knows whether there was conscientious breeding behind a dog with a problem or not. All breeders are not equal. Consientious breeders often spend a life time making improvements in their line of dogs. And we don't know what Willis meant with regard to that successful line of Boxers. If they were all keeling over as young dogs or collapsing in the ring they wouldn't have been able to have long-time success in the show ring - that takes healthy, well-structured dogs. As for COI's, the further one goes back the more similar the pedigrees will become since one is getting into the founding stock and the number becomes meaningless, due to being inflated. The COI is but one piece of information to consider when breeding a pair of dogs, much more important is the use of healthy, sound dogs for breeding. Purebreds are purebreds and there are some people out there that seemingly do want purebred dogs to be mongrelized. Clearly breeds are going to have higher COI's than mixed breeds and as far as I am concerned people are just going to have to accept that that is the nature of purebred dogs - they are going to have higher COI's and they are going to be more related than mixed breeds, and none of this means that it will be detrimental to the health of purebred dogs. Genetic problems still come down to gene combinations, independent of level of COI. Low COI's influence probability on average but a conscientious breeder can influence probability more effectively with careful selection. And my remark about being able to always use cross-breeding in the future was meant facetiously. The point is that we have outsiders screaming for the studbooks to be opened now, even for breeds that have not been shown to be in trouble, basically putting the cart before the horse. Cross-breeding will always be an available last resort if it comes down to it. And many breeds may never reach that point. DNA testing may catch up in time to help identify carriers of serious problems. Even if cross-breeding really becomes necessary and is implemented, just how helpful would bringing in a handful of dogs actually be? How would one control those dogs from bottle-necking the breed, should all breeder (unlikely) choose to breed to the cross-bred dogs? The popular sire effect all over again with a handful of cross-breds. More likely there will be a good-sized proportion of the fancy that will be diehards and refuse to use the cross-bred dogs and carry on with their now even more limited breeding population. Doesn't look to be much of a solution. Dog breeds deserve a great deal more thought than the hysterical ravings of geneticist-wannabes or the uninformed conclusions of geneticists with absolutely no understanding of the structure of breeds and the vast differences between the motivations of breeders. The situation is so much more complicated than most of these people realize, and therein lies the danger.

Christopher said...

I enjoy that you bring up the Dalmatian as an example of how easily we can go find a gene that has been removed from a given population and work it back into the gene pool to restore diversity and health.

I'll note that despite the huge effort, incredible expense, and years of time put into fixing just one gene in the Dalmatian, that the breed club has refused to register these dogs that are 99.99% Dalmatian.

Could you please provide an example of which show breeds have allowed in new blood from another breed for any reason at all: health, genetic diversity, whim?

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Papa Giorgio said...

I have a question -- hypothetical. Let's say that [if it were possible] to kill all Canidae, except for Chihuahuas, could you ever breed back up to wolves or other "parent" populations?