The costs and benefits of inbreeding.

[Officially Retired]

Okay, I will address this article as best as I can, with what time I have. While I do not have a degree in Canine Biology, I do have over 20 years experience actually breeding, maintaining, and keeping competitive a single family of dogs ... and, most importantly, I have kept them in the winner's circle ... all over the world ... wherever they get off the plane. So I will address what is basically an interesting article, a true article, and yet one that has NO PERSPECTIVE from a performance standpoint ... and also overlooks some other key issues. With that preamble out of the way, here goes:

This is an interesting piece I came across. (if you can get your head around it, I had to read it a few times)
It's written by Carol Beuchat PhD of the institute of canine biology.

I agree. It is extremely interesting, it shows a great knowledge of the truths of line/inbreeding, but yet it also comes from a dispassionate (non-performance) perspective ...

I thought I'd share on here as I know a lot of guys have a real interest in this subject and research.
I believe some of the findings show the real difference between the vigour of our bulldogs and a lot of other breeds.

Follow the link for the full article with all charts.

http://www.instituteofcaninebiology....-of-inbreeding

Thank you for the link and discussion

Even 100 years ago, the costs and benefits of inbreeding were understood, and even if the mechanisms weren't fully understood, breeders knew from experience that there were tradeoffs. The Coefficient of Inbreeding was formulated specifically to serve as a tool to quantify these risks and benefits in a way that could be used in making breeding decisions. (See Wright's Coefficient of Inbreeding)
It's easy to make the lists:

Yes, anyone who has ever succeeded, long-term, reliably and consistently, as a breeder **IS** a family breeder by default. It is simply impossible to succeed as a breeder playing guessing games with "random possibilities"; you MUST limit your surprises through minimizing variance, and you MUST be selective in the individuals you choose to use.

ADVANTAGES

increased uniformity
increased prepotency (ability to pass on traits to offspring)
“fixing” of desired traits and breed type

DISADVANTAGES

lower fertility
lower “vigor”
birth defects
smaller size
fewer offspring
slower growth
higher offspring mortality
shorter lifespan
increase in genetic diseases
reduced “genetic potential” (ability to improve a trait)

I have experienced every single one of these benefits/liabilities first-hand. Every single one.

But, here again, the key to limiting the disadvantages, while retaining the advantages, is SELECTION. I have made some bad choices, like anyone else, but for the most part I would get rid of dogs that had too many health issues. Furthermore (and this hasn't even been discussed by the author, but which is absolutely VITAL) is what you feed your stock therefore becomes that much more significant. The Hollingsworth dogs already had SEVERE cancer likelihoods, and I experienced first hand the deaths (and decreased fertility) of many great dogs early on (Poncho, Stormbringer, Wild Red Rose, etc.) These were fucking GREAT dogs that died too young, and stopped producing too young, PRECISELY BECAUSE they were fed shit-kibble most of their lives.

Thus the lower fertility/lifespan of these dogs, and their propensity to suffer cancers, was directly linked to what they were being fed

This means, while you may get away with feeding mixed-bred mutts cheaper feed, you can NEVER make them produce as consistently as linebred animals. Never. However, while linebred animals may have some liabilities, you CAN control this through your feeding practices.

I have always likened this comparison to cars: a Ferrari may never last as long as a Toyota, and you may not be able to run it on "cheap gas"; however, if you step up to the plate and buy a Ferrari, and put the right gas in it, you will enjoy your driving experience a whole lot more. But if you get the car, and put cheap gas in it, don't expect it to last very long. It will never perform its best that way--and (as with feeding inbred dogs shit-kibble) expect a lot of trouble.

However, when given the proper gas, and kept in optimal conditions, there are simply awesome benefits to Ferrari ownership that cannot be measured in "how long it lasts" ... exhilarating benefits that "owning a Toyota for 20 years" will never give you

Why does inbreeding increase uniformity and prepotency?
Inbreeding increases homozygosity. By that, we mean that if there are two (or more) alleles in the population for a gene, the frequency of AA and aa will increase, and Aa and aA will decrease. If a dog is homozygous for AA, then it can ONLY pass the A allele on to its offspring - it is "fixed" for the A gene. The greater the degree of homozygosity of an animal's genome, the more uniform its offspring will be because they will all get the same allele for many genes from that parent. If you are trying to breed for specific traits, this is a huge advantage. Variation among litter mates will be reduced, and the inbred parent will be said to be "prepotent" - it creates offspring with a recognizable "look".

Nicely put. And, when well-selected, that prepotency does more than produce a uniform "look," it also produces more uniform performance expectations

This would all be good except that nature doesn't especially like homozygosity. In hundreds of studies, in many different species both plant and animal (including domestic animals), there is irrefutable evidence that homozygosity comes with a price. Wright noted that

"...it may be readily shown that the decrease in vigor in starting inbreeding in a previously random-bred stock should be directly proportional to the increase in the percentage of homozygosity", and "As for the other effects of inbreeding, fixation of characters and increased prepotency, these are of course in direct proportion to the percentage of homozygosis."

What the article doesn't state (and what this woman doesn't even consider) is that, again, through proper selection, you can KEEP the fertility in your inbred animals: simply by choosing to use the pups from the biggest litters

In 20 years of line- and inbreeding dogs commercially, with an eye for performance, my selection abilities are going to be more acute than some woman breeding dogs who's only looking for "problems" or a "uniform look." Any idiot can do that, quite frankly. But keeping dogs GAME, ATHLETIC, and CAPABLE OF WINNING requires a little bit more scrutiny than what she is doing ... and when your livelihood depends on this ... AND keeping your litter sizes profitable ... I assure the reader my interest in ALL of the above was substantially more than "academic"

That said, I have had aspects of my line that could hardly produce 1 pup in a litter (mostly Coki dogs). I have also produced 9-pup litters from double-inbred animals being bred together. The KEY therefore, to everything, really, is SELECTION

What is NOT being discussed is the THE FACT that some inbred animals will not only BE better as individuals, but some will also be MORE FIT and MORE FERTILE than others as well ... therefore, here again, if the family breeder selects for those individuals who are more fertile, he can keep the fertility of his line intact.

Dairy goats are inbred and selected for producing more milk; you can inbreed and select for anything you want.

The trouble (in our sport) arises when we have a "conflict of interests," when a great performer has some genetic defect, what to we do? A classic example would be Ch Robert T Jr. Here was a dog that beat four 4xWs, who stopped 4 dogs from making Grand Champion, and his owner never bred him. Why? Because Robert T Jr. had "mangy feet" ...

This kind of stupidity is why people fail as breeders (and is why this particular individual always had to BUY his great dogs and could never produce them). You have to have the sense to understand what is a BAD defect and what is a defect that DOESN'T MATTER. I mean, who gives a fock about mangy feet, if the dog is capable of beating anything with hair on it and winning hundreds of thousands of dollars in money

More important still is, again, enough ALL AROUND KNOWLEDGE to control mangy feet by feeding better feed

While Heinz 57 mutts might get away being fed corn-based kibble, many high-performance animals canNOT. So, here again (and I say this with half-a-lifetime of real-world experience), IF PEOPLE WOULD JUST UP THEIR OWN OWNERSHIP EFFORTS, AND FEED THE BEST FEED POSSIBLE a lot of these "defects" of mange and cancers will go away ... or at least be drastically-improved.

For example, my Wild Red Rose bitch (fed kibble) died of cancer at only 5 years of age. Yet her double-inbred daughter Sassy (fed kibble half her life, raw the other half) died of cancer at over 10 years of age. As Sassy actually has a higher COI than her mother Rosey, this means my more inbred bitch had more "fitness" than her mother, just by my changing diets. This is why I am such a stickler on canine nutrition, and why I call everyone a "retard" who doesn't feed the best they can. They're fogging up, basically, and too clueless/lazy to benefit from real-life experience being spoon-fed to them.

This is illustrated in these figures. "Fitness" is a measure of an animal's ability to produce offspring that can contribute genetically to the next generation. Producing offspring that don't themselves produce offspring gives you a fitness of zero. It might be that the offspring are infertile, or died after birth, or were too slow or too stupid to outrun a predator - doesn't matter, the measure of interest is whether an animal's genes will stay in the gene pool through the next generation.
When the COI is zero, fitness is at its maximum and prepotency and uniformity are at their lowest. As inbreeding increases, variation in the offspring goes down but so does fitness.

Ahh, this is where the article digresses from the interests of a sporting breeder into the "cerebral nonsense" of an academic.

My goal was NOT to produce pups "that can produce more pups"; my goal was to produce pups that can be COUNTED ON to win and/or produce winners. I would rather have only 4 pups in a litter whom I could depend on to BE GAME, and may have to be fed top-notch feed, than I would to produce 10 pups that I can get away with feeding them shit, but who will quit the moment they fall behind.

So you really have to keep your eye on the ball, as a reader, because the writer HAS NO CLUE about breeding for performance. Her eye is on the "fitness" ball (as far as disease resistance/fertility goes), but there is another "fitness ball" to keep your eye on, and that is the ability to reliably and consistently kick ass and be game.

If I have kept my dogs GAME, SMART, and GOOD, then I do not ever want to introduce "variety" in that

That is the whole freaking point of keeping a family pure, is when you get to the point of not getting "variety" (unpleasant surprises) in what you're reliably and consistently able to produce.

Further, you keep your "fitness" intact by selecting for those individuals who ARE fit and who CAN produce.

That is the entire goal (dare I say JOB?) of the family breeder: to select for desirable traits and navigate around undesirable traits

Inbreeding reduces fitness (the red line), and the decrement in fitness is proportional to the degree of inbreeding. This reduced fitness is called "inbreeding depression", which is a catch-all for all things that play a role in reducing fitness. If you start with an outbred plant (so high heterozygosity) that self-pollinates (self-fertilization, so we don't have to worry about the genetics of the mate), germination of the seeds produced will be reduced. As you continue to self-pollinate successive generations, the reduction in germination is proportional to the inbreeding coefficient and therefore the amount of homozygosity (blue line).

Well, I don't know about flowers and all, but I have had MANY inbred dogs that not only were game, and propotent, but that also were VERY fertile: Duke Nukem would be such a dog.

This is a very handy relationship. The cost and benefit of inbreeding are directly proportional to the COI. This means that a breeder can choose a level of inbreeding that is a good balance between cost and benefit.
Inbreeding depression in dogs
Are there data that show a negative effect of inbreeding depression in dogs?
Here are some data on litter size of 6 breeds of dogs from the records of the Swedish Kennel Club. The first thing I would warn about is that these are probably 10 generation COIs, which we already know are likely to underestimate the true COI especially for breeds that have been around for a while (e.g., Goldens and Labradors). So understand that the placement of these lines relative to each other and the X axis is not likely to be the "truth".

Here is exactly why you CAN'T follow "data on a graph" all the time. It may not apply to your dog.

Just because I have a dog that is 75% "bred like Poncho" on paper doesn't MEAN my dog is "just like Poncho" ... he may not resemble my foundation dog in ANY way ... and yet a 56.25% Poncho dog may be his genetic clone. Or maybe the 75% dog's littermate is the true Poncho dog. Again, this is where SELECTION comes in ... and that selection should never come from some freaking graph, or pie chart, it should come FROM YOUR EYES and (hopefully) some good common sense

For our purposes, however, it doesn't really matter. What we want to see is the effect of COI on litter size, and as observed by Wright and many others, the reduction in litter size as inbreeding increases is linear.

The slopes of these lines tell us exactly what this "cost-benefit" ratio is. For these breeds, those slopes are about 0.1, which means that an increase in inbreeding of 10% reduces litter size by about 1. If normal litter size is about 6, a COI of 30% - which is not uncommon in many breeds - would reduce the litter size by HALF. That is half as many offspring from which to choose your "pick", and on top of this realize that these puppies will have reduced fitness in the ways noted by Wright - they are likely to be smaller, less vigorous, have more birth defects and higher mortality, grow more slowing, have shorter lifespan, and of course increased incidence of genetic disorders caused by recessive mutations.

Again, this is all theoretical "on average" bullshit.

There will ALWAYS be exceptions, some worse than what "the graph" relates, some better than what the graph relates. Not every dog follows every likelihood. This is why scientists like this are never actual breeders of excellence, they pay too much attention to "graphs," in relative terms, and do not look for INDIVIDUAL EXCELLENCE ... which is precisely the job of the family breeder: forever selecting for individual excellence amongst the group

How is inbreeding depression manifested in offspring? The impact on puppy mortality is clear. These data for Beagles unfortunately pool together all the dogs with COI less than 25% (so we can't see whatever effect there , but the average mortality by 10 days for this group was greater than 20%. As inbreeding increases above 25%, the mortality increases, to about 30% for dogs with COI between 25-50%, and higher still as COI increases.
In Standard Poodles, dogs with inbreeding less than 6% live 4 years longer than those with higher COI, and the risk of bloat is roughly proportional to the increase in COI - a 10% increase in COI elevates the risk of bloat by about the same amount.
In Bernese Mountain Dogs, each 10% increase in COI reduces lifespan by 200 days. For a dog with COI of 30%, that's a reduction in lifespan of almost two years.

But what does any of this have to do with performance dogs? Okay, maybe my triple-bred Ch Hammer dog, Silverback, only lived to 10 years old. But 1) he stayed fertile his entire life, until 2 months before he died, and 2) if I could bring any male dog back from the grave I have ever owned in my life HE would be the one ... not some 17-year old mix-bred mutt somewhere else "that I could feed kibble to" just to avoid having to make good dog food.

I don't need to decrease the gameness/ability % in my dogs, to stretch their lifespans from 10-12 years, on up to 15-17 years. That has no importance to me whatsoever, as a breeder of performance excellence. Again, this is taking one's eye "off the ball" and concentrating on minutia.

The thing I care about most of all is reliable and consistent gameness and ability in my animals, NOT whether they have 4 pups or 12 pups in their litters, or whether they live 10 years or 15 years, and the kind of performance reliability and consistency I get can ONLY be maintained at the level I am accustomed to via FAMILY BREEDING. It will never happen making random mixes forever "to keep my resistance to disease" low or my "number of pups per litter" high.

So, again, this woman may be speaking the truth, but her VALUES are different from mine, as a performance dog breeding specialist.

So how much inbreeding is too much?
Now that's the million dollar question. If inbreeding was only good, animal breeders would be merrily inbreeding and the animals would be thriving. But most animal (and plant) breeders go to some pains to manage inbreeding, and for reasons like the ones above. So how do you evaluate the costs against the benefits?

It is very easy to answer this, Lady-Genius: Inbreeding is "too much" ONLY when it produces animals that can neither win, nor produce winners, and that will ONLY happen when the wrong dogs are selected for the mating, NOT because of the "inbreeding" itself

THE KEY to everything bad, and good, will always be SELECTION

The rule of thumb for sustainable breeding of both wild and domestic animals is to keep inbreeding below 5%, and to consider 10% an upper limit for a population. There might be occasional animals that are much higher than this (for example, in maintaining multiple herds to use for outcrossing within a line), but when the population average goes higher than about 10% things begin to go downhill. As fertility goes down and litters get smaller, there are fewer animals born each generation, and those that are have an increased risk of genetic disorders, shorter lifespans, and general lack of vigor. This becomes a negative feedback loop that is called "the extinction vortex", and once a population heads down this path it can be very difficult to stop. Note again, that threshold for this vortex phenomenon is about COI = 10%. For most livestock breeds being bred sustainably, inbreeding is kept well below this. Organization breeding guide and service dogs keep inbreeding below 10%. But among purebred dogs otherwise, a COI (calculated back to founders) could be very difficult to find. And evidence of inbreeding depression and the other consequences of inbreeding are very evident - singleton litters, high rates of cancer in young dogs, allergies, and many other issues that seem to be "normal" in the breeding of dogs these days.

This is all theoretical bullshit that has NOTHING to do with breeding for performance. If you want to find "fitness" ... if you want to find "excellence" ... then you have to look at THE DOGS PRODUCED ... and SELECT FOR these things ... and you will never find your answers on a graph or a pie chart ... you MUST look at the actual dogs ... and you must SELECT the right ones. Breeder competence, breeder knowledge, and breeder dedication MEAN EVERYTHING ... and you cannot measure this on a graph or pie chart.

Inbreeding can be used to produce exceptional animals, but the cost is very real.

And the cost of clueless people randomly breeding dogs together ... with no discrimination, no game plan, nor any desire to achieve genetic uniformity ... is even more real.

Jack