I'm a breeder who has practiced linebreeding for 10 years, several generations, with a few (rather disappointing) outcrosses thrown in. Since late November, I've been studying diversity theories giving it considerable thought. Sometimes in the process of debating the merits of continuing the way I have been versus striving for genetic diversity (or something in between) I feel like I'm going around in circles in my attempt to determine what the best way to breed dogs actually is.
This whole idea of suppressor genes and their possible role in minimizing the expression of serious health defects is worthy of consideration as well. The thought they may be line or strain specific is almost frightening. Makes striving for diversity not sound as easy to me anymore -- it's not so much a matter of "what harm can it do to try."
So while I'm not *thoroughly* convinced that genetic diversity is better, or that if we all don't change our breeding practices purebred dogs are doomed, I must say I'm still strongly leaning in that direction. Here are some thoughts that run through my mind in this regard. I'd be interested in knowing how other breeders who are currently where I am with regard to seriously considering making changes in how they breed dogs feel about the issues. I'm hoping others will share their own thoughts, experiences, and observations for the benefit of all.
It seems to me the problem with this is *most* genepools or strains *don't* hold up at COI's as high as 40%. (That has certainly been my experience.) So if we continue to linebreed, increasing COI with each generation, inadvertently (or perhaps better said ignorantly) accumulating non-visible alleles that impair function each step along the way, selecting against those sub-populations or genepools who can't hack it, aren't we basically just further limiting our choices of genetic material to work with? Where to go when something goes awry (which it will) and there are no options within the population to correct the problem?
Inevitably, weeding out or selecting against the "less than fit" familial bred strains will increase the COI beyond that 40% mark in short order (if you only have a few strains to work with.) Most assuredly at some point the small minority of strains that hold up at 40% COI aren't going to hold up for long at higher COIs. They *are* eventually (sooner rather than later beyond COIs of 40% IMHO) going to exhibit the effects of inbreeding depression as cumulative inbreeding and the impact of concentrating higher numbers of suboptimal alleles increases with each generation. Seems to me it can't go on like this indefinitely, there won't be anything "fit" left to breed together.
The old concept of linebreed for two or three generations then outcross for hybrid vigor (*if* you can accomplish a true outcross within your breed) is probably better than simply practicing linebreeding alone as it will slow things down somewhat. That said, I now see there are ways to slow things down more dramatically. If we accept that inbreeding depression is a fact, we can easily reconcile and accept the more we slow down the inbreeding process, the better off an entire breed will be for a longer period of time.
The sticky wicket with accepting the "diversity theory" seems to be this idea we have ingrained in our heads that "less alleles to deal with is better". Why can't we let go of this? Just for a moment, erase from your mind all you've learned in the past from books and mentors on dog breeding and use your common sense. Humans don't breed like this. Do we honestly think this is merely because of the social stigma associated with incest? I think we can all agree that historically, inbred human strains are less fit, less healthy, and less likely to be viable long term. Yet as dog breeders, we tend to look at a pedigree and see a significant genetic contribution from one or more of our "favorites" two, three, and more generations back multiple times, resulting in a relationship coefficient as high as 30-60% (potentially contributing as much or more than a parent) and we get all excited about this. We view it as a wonderful thing that this animal in front of us can only pass on a very limited combination of alleles. We feel quite proud that we have affected this result. Well, another way to look at it is the linebred animal in front of us doesn't have much genetic material to offer.
Even inbred strains of lab mice that allegedly endure the rigors of generations of inbreeding (and that is only perhaps 10-20% of strains that don't become extinct I believe) do not apparently have optimally functioning immune systems, i.e, "can't hack it" outside a sterile and controlled laboratory environment.
I've practiced linebreeding for years; I know full well what the advantages are and how easy it is in many ways to achieve predictability, and I've enjoyed my successes in that manner. My track record for common health defects in my primary breed, Great Pyrenees, is impeccable. My rate of defects is less than 2-5% for any health issue reported in our breed wide health survey. However, while my incidence of health defects as such seems admirably low (and I'm not seeing an increase in these areas) I *am* beginning to see other subtle signs of problems in the reproductive and immune system departments that concern me.
That said, I'm now kind of "hanging my hat" on maximum variation of MHC genes being a *key* component of long term survival. This is what is convincing me that continued linebreeding is likely not the way to go. I'm not sure it's a realistic goal to achieve maximum heterozygosity of MHC genes and minimum heterozygosity of virtually everything else. Maybe I'm wrong. Maybe this is an angle to pursue.
The way I'm beginning to see things now is it's better safe to work on the assumption that all species and populations are doomed to extinction (eventually) due to either natural selection (some of which may be beyond control) and/or intervention (either lack of intervention, i.e, medical intervention to prolong life, or inappropriate purposeful intervention, i.e., improper management of long-term species survival -- manipulating the selection process in a manner that "goes against nature.")
If we work from this assumption that all populations are doomed to extinction (okay, so I'm feeling a little "doomsdayish" today) what we do by manipulating the selection process is either shorten or lengthen the time it takes to reach that inevitable destination. We can intervene in a manner that may possibly delay the inevitable, or we can intervene in a manner that accelerates our arrival there. If we consider the members of a population of any purebred strain of dogs (a breed) are genetically related to some degree as compared to members of two very different breed populations who share no founders, doesn't it make sense to slow this process down as much as possible by breeding the most distantly related mates we can within a breed, and continuing in that manner as long as we possibly can in order to ensure long-term viability?
I *think* I'm starting to see subtle signs of inbreeding depression in my successive generations of "softly" linebred strain of Great Pyrenees at COIs somewhere between 20 and 30%. I classify softly linebred as mainly cousin matings, aunt-nephew, uncle niece, cousins generations removed, other familial relationships further removed. I never used to lose puppies (in my first few years of breeding.) Now, I have at least one stillborn or early neonatal death in almost every litter. My bitches never used to "miss". Now, I'd say close to 25% of my bred bitches don't conceive on first attempt at breeding them. (Most have conceived on subsequent matings to different males.) I am aware of too many males in the line who WILL NOT breed naturally, must be collected and the bitches AI'd. I'm seeing a more noticeable number of vaccine reactions in puppies of this line. I'm seeing noticeable occurrences of vaccinated puppies contracting parvo in this line. I'm seeing a slight increase in allergies and related chronic ear/skin issues in this line. I'm seeing a higher incidence of impaired thyroid function in this line.
On the plus side of linebreeding, as mentioned earlier, I've had virtually no incidences of the most commonly accepted hereditary health defects in the breed, i.e., CHD, patellar luxation, cardiomyopathy, epilepsy, to name a few (the biggies). I've successfully produced a stable, even tempered animal that is not more of a challenge to an owner than it should be, nor is it a threat or menace to society. This has been with a fair amount of consistency. However, I've had a few outliers here and there, a few "skittish" temperaments and a few overly aggressive temperaments. I haven't really seen concerning aggressive tendencies towards humans, rather towards other animals. Regardless, I'd rather not see those numbers of skittish and aggressive temperaments start to increase. I'm wondering if that too is not an inevitable affect of continued familial breeding (unstable temperaments.)
I'm relatively inexperienced in my other breed, Belgian Shepherds. Don't have much practical breeding experience to go on. However, I've made quite a few observations, gathered a tremendous amount of data, and spent hundreds of hours studying and analyzing numbers. I've made a point to familiarize myself with the history of the breed and varieties, how the various populations and subpopulations across the world developed, and how they've changed over the last 100 years. Based on all of this, it seems to me in Belgians (at least the long haired varieties Tervuren & Groenendael) we begin to see signs of impaired immune system and reproductive function at COIs as low as 15% in at least half the strains, probably more. Seems to be an increase in reports of autoimmune diseases. Rate of epilepsy is definitely too high for comfort, CHD and OCD seem to be slightly on the rise, various eyes defects are plentiful and known, but *appear* to be somewhat under control. Certain strains of Belgians obviously have lower incidences of some defects and higher incidences of others, so what concerns me is this idea of "suppressor" genes and their roles in all of this. What's going to happen as these lines are crossed in an effort to achieve more diversity if a number of suppressor genes are at play here and existent in some lines but not in others?
Considering what I can discern in my two breeds I can't help but notice some things aren't quite right here. I think we have to do "something" before things get any worse, and I think before *I* embark on my Belgian Shepherd breeding program in earnest, I want to have some diversity goals in mind. I feel like the ugly truth is staring me in the face and things aren't going to improve if I start out breeding Belgians following the same path I've followed for almost 10 years in Great Pyrenees. I know from my study of historical accounts of Belgians, the founding basis in the US (this country at least, maybe more) is much smaller, less diverse, and less fit than the founding basis in Great Pyrenees. So here I sit, thinking about all of this, trying to formulate a plan and figure out how I should get started in Belgians and how I should change the way I breed Great Pyrenees. Then I start to wonder is their really a simple right and wrong answer? Is the proper balance somewhere in the middle?
Here's a thought that has puzzled me and I hope someone can shed some light on it. Surely we can all agree that linebreeding is merely a modified form of inbreeding, just slows down the inevitable. If we are such great proponents of linebreeding as the preferred method, why don't we just skip the linebreeding and go straight to inbreeding (successive generations of sib matings) with stringent selection? Can someone who is experienced with and has successfully practiced generations of linebreeding answer that question for me? If linebreeding is so good, such a great way to get where you want to be and increase predictability, why not practice close inbreeding instead?
Maybe for those who are undecided, the missing piece to this whole puzzle lies in the answer to that question.
Kelley Hoffman <kshoffman@aol.com>
BasqueLaine Kennel
Great Pyrenees & Belgian Shepherds
I'm a breeder who has practiced linebreeding for 10 years, several generations, with a few (rather disappointing) outcrosses thrown in. Since late November, I've been studying diversity theories giving it considerable thought. Sometimes in the process of debating the merits of continuing the way I have been versus striving for genetic diversity (or something in between) I feel like I'm going around in circles in my attempt to determine what the best way to breed dogs actually is.
This whole idea of suppressor genes and their possible role in minimizing the expression of serious health defects is worthy of consideration as well. The thought they may be line or strain specific is almost frightening. Makes striving for diversity not sound as easy to me anymore -- it's not so much a matter of "what harm can it do to try."
So while I'm not *thoroughly* convinced that genetic diversity is better, or that if we all don't change our breeding practices purebred dogs are doomed, I must say I'm still strongly leaning in that direction. Here are some thoughts that run through my mind in this regard. I'd be interested in knowing how other breeders who are currently where I am with regard to seriously considering making changes in how they breed dogs feel about the issues. I'm hoping others will share their own thoughts, experiences, and observations for the benefit of all.
It seems to me the problem with this is *most* genepools or strains *don't* hold up at COI's as high as 40%. (That has certainly been my experience.) So if we continue to linebreed, increasing COI with each generation, inadvertently (or perhaps better said ignorantly) accumulating non-visible alleles that impair function each step along the way, selecting against those sub-populations or genepools who can't hack it, aren't we basically just further limiting our choices of genetic material to work with? Where to go when something goes awry (which it will) and there are no options within the population to correct the problem?
Inevitably, weeding out or selecting against the "less than fit" familial bred strains will increase the COI beyond that 40% mark in short order (if you only have a few strains to work with.) Most assuredly at some point the small minority of strains that hold up at 40% COI aren't going to hold up for long at higher COIs. They *are* eventually (sooner rather than later beyond COIs of 40% IMHO) going to exhibit the effects of inbreeding depression as cumulative inbreeding and the impact of concentrating higher numbers of suboptimal alleles increases with each generation. Seems to me it can't go on like this indefinitely, there won't be anything "fit" left to breed together.
The old concept of linebreed for two or three generations then outcross for hybrid vigor (*if* you can accomplish a true outcross within your breed) is probably better than simply practicing linebreeding alone as it will slow things down somewhat. That said, I now see there are ways to slow things down more dramatically. If we accept that inbreeding depression is a fact, we can easily reconcile and accept the more we slow down the inbreeding process, the better off an entire breed will be for a longer period of time.
The sticky wicket with accepting the "diversity theory" seems to be this idea we have ingrained in our heads that "less alleles to deal with is better". Why can't we let go of this? Just for a moment, erase from your mind all you've learned in the past from books and mentors on dog breeding and use your common sense. Humans don't breed like this. Do we honestly think this is merely because of the social stigma associated with incest? I think we can all agree that historically, inbred human strains are less fit, less healthy, and less likely to be viable long term. Yet as dog breeders, we tend to look at a pedigree and see a significant genetic contribution from one or more of our "favorites" two, three, and more generations back multiple times, resulting in a relationship coefficient as high as 30-60% (potentially contributing as much or more than a parent) and we get all excited about this. We view it as a wonderful thing that this animal in front of us can only pass on a very limited combination of alleles. We feel quite proud that we have affected this result. Well, another way to look at it is the linebred animal in front of us doesn't have much genetic material to offer.
Even inbred strains of lab mice that allegedly endure the rigors of generations of inbreeding (and that is only perhaps 10-20% of strains that don't become extinct I believe) do not apparently have optimally functioning immune systems, i.e, "can't hack it" outside a sterile and controlled laboratory environment.
I've practiced linebreeding for years; I know full well what the advantages are and how easy it is in many ways to achieve predictability, and I've enjoyed my successes in that manner. My track record for common health defects in my primary breed, Great Pyrenees, is impeccable. My rate of defects is less than 2-5% for any health issue reported in our breed wide health survey. However, while my incidence of health defects as such seems admirably low (and I'm not seeing an increase in these areas) I *am* beginning to see other subtle signs of problems in the reproductive and immune system departments that concern me.
That said, I'm now kind of "hanging my hat" on maximum variation of MHC genes being a *key* component of long term survival. This is what is convincing me that continued linebreeding is likely not the way to go. I'm not sure it's a realistic goal to achieve maximum heterozygosity of MHC genes and minimum heterozygosity of virtually everything else. Maybe I'm wrong. Maybe this is an angle to pursue.
The way I'm beginning to see things now is it's better safe to work on the assumption that all species and populations are doomed to extinction (eventually) due to either natural selection (some of which may be beyond control) and/or intervention (either lack of intervention, i.e, medical intervention to prolong life, or inappropriate purposeful intervention, i.e., improper management of long-term species survival -- manipulating the selection process in a manner that "goes against nature.")
If we work from this assumption that all populations are doomed to extinction (okay, so I'm feeling a little "doomsdayish" today) what we do by manipulating the selection process is either shorten or lengthen the time it takes to reach that inevitable destination. We can intervene in a manner that may possibly delay the inevitable, or we can intervene in a manner that accelerates our arrival there. If we consider the members of a population of any purebred strain of dogs (a breed) are genetically related to some degree as compared to members of two very different breed populations who share no founders, doesn't it make sense to slow this process down as much as possible by breeding the most distantly related mates we can within a breed, and continuing in that manner as long as we possibly can in order to ensure long-term viability?
I *think* I'm starting to see subtle signs of inbreeding depression in my successive generations of "softly" linebred strain of Great Pyrenees at COIs somewhere between 20 and 30%. I classify softly linebred as mainly cousin matings, aunt-nephew, uncle niece, cousins generations removed, other familial relationships further removed. I never used to lose puppies (in my first few years of breeding.) Now, I have at least one stillborn or early neonatal death in almost every litter. My bitches never used to "miss". Now, I'd say close to 25% of my bred bitches don't conceive on first attempt at breeding them. (Most have conceived on subsequent matings to different males.) I am aware of too many males in the line who WILL NOT breed naturally, must be collected and the bitches AI'd. I'm seeing a more noticeable number of vaccine reactions in puppies of this line. I'm seeing noticeable occurrences of vaccinated puppies contracting parvo in this line. I'm seeing a slight increase in allergies and related chronic ear/skin issues in this line. I'm seeing a higher incidence of impaired thyroid function in this line.
On the plus side of linebreeding, as mentioned earlier, I've had virtually no incidences of the most commonly accepted hereditary health defects in the breed, i.e., CHD, patellar luxation, cardiomyopathy, epilepsy, to name a few (the biggies). I've successfully produced a stable, even tempered animal that is not more of a challenge to an owner than it should be, nor is it a threat or menace to society. This has been with a fair amount of consistency. However, I've had a few outliers here and there, a few "skittish" temperaments and a few overly aggressive temperaments. I haven't really seen concerning aggressive tendencies towards humans, rather towards other animals. Regardless, I'd rather not see those numbers of skittish and aggressive temperaments start to increase. I'm wondering if that too is not an inevitable affect of continued familial breeding (unstable temperaments.)
I'm relatively inexperienced in my other breed, Belgian Shepherds. Don't have much practical breeding experience to go on. However, I've made quite a few observations, gathered a tremendous amount of data, and spent hundreds of hours studying and analyzing numbers. I've made a point to familiarize myself with the history of the breed and varieties, how the various populations and subpopulations across the world developed, and how they've changed over the last 100 years. Based on all of this, it seems to me in Belgians (at least the long haired varieties Tervuren & Groenendael) we begin to see signs of impaired immune system and reproductive function at COIs as low as 15% in at least half the strains, probably more. Seems to be an increase in reports of autoimmune diseases. Rate of epilepsy is definitely too high for comfort, CHD and OCD seem to be slightly on the rise, various eyes defects are plentiful and known, but *appear* to be somewhat under control. Certain strains of Belgians obviously have lower incidences of some defects and higher incidences of others, so what concerns me is this idea of "suppressor" genes and their roles in all of this. What's going to happen as these lines are crossed in an effort to achieve more diversity if a number of suppressor genes are at play here and existent in some lines but not in others?
Considering what I can discern in my two breeds I can't help but notice some things aren't quite right here. I think we have to do "something" before things get any worse, and I think before *I* embark on my Belgian Shepherd breeding program in earnest, I want to have some diversity goals in mind. I feel like the ugly truth is staring me in the face and things aren't going to improve if I start out breeding Belgians following the same path I've followed for almost 10 years in Great Pyrenees. I know from my study of historical accounts of Belgians, the founding basis in the US (this country at least, maybe more) is much smaller, less diverse, and less fit than the founding basis in Great Pyrenees. So here I sit, thinking about all of this, trying to formulate a plan and figure out how I should get started in Belgians and how I should change the way I breed Great Pyrenees. Then I start to wonder is their really a simple right and wrong answer? Is the proper balance somewhere in the middle?
Here's a thought that has puzzled me and I hope someone can shed some light on it. Surely we can all agree that linebreeding is merely a modified form of inbreeding, just slows down the inevitable. If we are such great proponents of linebreeding as the preferred method, why don't we just skip the linebreeding and go straight to inbreeding (successive generations of sib matings) with stringent selection? Can someone who is experienced with and has successfully practiced generations of linebreeding answer that question for me? If linebreeding is so good, such a great way to get where you want to be and increase predictability, why not practice close inbreeding instead?
Maybe for those who are undecided, the missing piece to this whole puzzle lies in the answer to that question.
Kelley Hoffman <kshoffman@aol.com>
BasqueLaine Kennel
Great Pyrenees & Belgian Shepherds