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                                                                                     COI and Inbreeding

 To figure your dogs COI go here:  (COI)


The level of inbreeding is usually measured using a formula called Wright’s Coefficient of Inbreeding.(COI)

 It calculates the probability that genes may have been inherited from both sides of an individual’s pedigree. It is far too complex to do by hand over more than two or three generations, but some of the better pedigree software will calculate coefficient of inbreeding (COI) for you. The usual 3-5 generation pedigree won't give sufficient information for a useful calculation.  The best indicator for calculating inbreeding COI is 10 generations.

A Good Reason for not inbreeding: Low Genetic Variation:

 Genetic variation is the raw material of evolution. Without genetic variation, a population cannot evolve in response to changing

environmental variables and, as a result, may face an increased risk of extinction. For example, if a population is exposed to a new disease,

selection will act on genes for resistance to the disease if they exist in the population. But if they do not exist—if the right genetic variation is

not present—the population will not evolve and could be wiped out by the disease.

 As an endangered species dwindles, it loses genetic variation—and even if the species rebounds, its level of genetic variation will not.

Genetic variation will only slowly be restored through the accumulation of mutations over many generations. For this reason, an endangered

species with low genetic variation may risk extinction long after its population size has recovered. Evolutionary theory suggests that, for the

long-term survival of a species, we need to conserve not just individual members of a species, but also a species’ ability to evolve in the face

of changing environmental variables—which means conserving individuals and genetic variation.

 When a species loses too many individuals, it becomes genetically more uniform and less adaptable to changing ecological conditions. 

Now one may ask what this means to domesticated pets?  Well if there was a deadly disease introduced and the population of dogs lacked

genetic variation there is a very good chance very few dogs would survive the epidemic.  Genetic Variation is vital in ensuring our breeds


 Incest, or inbreeding is forbidden on moral and legal grounds in most human cultures but the prohibitions also

make sense on from a biological sense. 

  Inbreeding depression is the loss of viability or function resulting from inbreeding. The signs of inbreeding

depression most easily identified as reproductive failures.  These reproductive failures may show themselves as

stillborn and deformed offspring, small litters, low sexual libido in the parent dogs, low sperm count in males while

females may fail to get pregnant, have unusually small litters, or exhibit poor mothering ability.

 Inbreeding depression may also manifest itself as poor health, temperament problems, mental health disorders, and

reduced ability to learn new tasks.

 Inbreeding depression can be manifested as a high frequency of immune-mediated diseases, significantly higher

incidence within a line or breed of one or more diseases than is seen in the species as a whole, or even things as

subtle as dogs that seem to catch every illness that comes along. In some cases, a very inbreed lines may go extinct. 

 The ideal COI for your dogs is anything under 15%. Above this level of inbreeding, an impact on the quality of the dog is felt heavily and increases exponentially as the inbreeding increases.  COIs under 15% have no negative impact on dogs.

 Common Relationships

  • 25.00% - parent/offspring or full brother/sister cross
  • 12.50% - half brother/sister, grandparent/grandpup, or double first cousins crosses
  • 9.75% - great uncle or aunt/great niece or nephew cross
  • 6.25% - first cousins

What is COI?

Technically, the COI is the probability that both genes of a pair in a dog are identical.  Simply put, it's a measurement of inbreeding.

It is calculated by a mathematical formula that is somewhat complicated to many users.  The function is...

COI = sum[ (.5 ^ (a + b + 1)) * (1 + c) ]

a = Generations between sire and common ancestor
b = Generations between dam and common ancestor
c = COI of common ancestor

If a common ancestor does not show up on both the top and bottom sides of a pedigree, it will not impact the COI of the dog.  Using this principle, you may breed a highly inbred bitch to a highly inbred dog and end up with hybrid offspring that do not have any inbreeding whatsoever.

Why does my dog that is the result of a father/daughter breeding have a COI higher than 25%?

If a common ancestor is inbred, it will increase the COI of its resulting offspring if they are inbred to it.



Written by Celeste Pongrácz

COI is the calculation of the level of inbreeding in a dog or
High COI percentages increase the probability that genetic
defects will be carried from common ancestors on both sides
of the pedigree and will match up to cause the actual genetic
disease or defect in the animal.
Many other problems of a high COI also affect dogs, such as
Autoimmune disease and inbreeding depression symptoms,
which result in reproductive and longevity issues.
A COI of 12.5% is equivalent to a half brother - half sister
mating or a grandparent - grandchild mating.
A COI of 25% is equivalent to a parent-child or brother -
sister mating.
Ideally, the COI of a litter should not exceed 6.25% or the
average COI of the two parents. It is highly recommended
to avoid COI percentages in excess of 12.5% and a COI in
excess of 20% should be totally avoided.
Some genetically inherited diseases and faults in
breeds are:
Hip and elbow dysplasia
Patella luxation
Eye disease such as: cataracts,
and Progressive Retinal Atrophy (PRA)
Allergies and skin problems
Retained testicles
Autoimmune diseases
Bad bites and missing teeth
Unacceptable colors
Temperament problems such as shyness and aggressiveness
Inbreeding depression symptoms are seen as the loss of
viability or function resulting from excess inbreeding.
Sometimes these symptoms are very subtle and gradual and
are often blamed on diet, pollution and other environmental
factors. While these factors may also contribute, it is the
dogs genes that make it more susceptible. The most
frequently seen inbreeding depression signs are:
Chronic poor health/poor keepers
Higher incidence of disease in a line (or breed) of one or
more diseases than is seen in the breed or canines as a
Higher incidence of immune system diseases
Unusually small litter size
Difficulty in getting and keeping bitches pregnant
Bitches that abandon a litter or are poor mothers
Bitches that kill or damage puppies intentionally or by lack
of care
Studs that are indifferent to a bitch in standing heat
Studs that cannot breed without help
Low sperm count
Earlier average age of death in a line or in the general breed
All of these factors make it incredibly important that you do
the COI calculation on any planned litter. Keeping the
breed healthy is easier than cleaning it up after the fact.
Once the gene pool is closed and the genetic base remains
the same, the genetic situation can either remain stable or
deteriorate, it cannot improve without new genetic material
brought in via outcrossing to another breed or the use of
non-registered stock.
Inbreeding, linebreeding and the usage of popular sires are
methods of the past ages of dog breeding, their time is over.
Nature goes to great lengths to avoid inbreeding, so should
today’s breeder. COI calculation can give the breeder an
indication of how inbred a dog or litter will be. Knowing
this percentage will enable you to make the best choices
towards reducing inbreeding in your dogs.
Today the emphasis should be put on health, temperament
and working ability if purebred dogs are going to survive
into the next hundred years. Active concern for health
should be your number one breeding goal, because without
health, you have no dog.
 You need to have all the dogs behind the pair you plan to mate for 10 generations
back in order to get the correct percentage as this is how far back the generations need to be taken into account.  You may not realize this, but 1 dog with 10 generations
behind it has 2046 dogs in its 10 generation pedigree! If you
want to calculate the COI of a pairing, you need to add in
2046 dogs from the one parent and 2046 dogs from the
other, that’s 4092 dogs.
10 generations may seem like a lot of generations and a lot
of dogs, but it is not and it is figured on a sliding scale with
the generations affect reducing by the proper proportions
as they recede. "Inbreeding was once a valuable tool in shaping today's
breeds. As these have now reached a high degree of
homogeneity, it has lost its importance and turned into a
fatal and disastrous habit." Hellmuth Wachtel, Ph.D.
"The breeding of purebred dogs is akin to (breeding
laboratory mice)...(most breeds) are becoming
progressively more inbred. My observation is that most are
on the road to extinction, but most breeders do not even
realize they are part of an experiment." John B.
Armstrong, Ph.D.
"However, we ignore the biological impacts of the practice
(inbreeding) at our peril - or more accurately, the peril for
our dogs." C.A. Sharp

More links below

Why Incest isn't Best by C.A. Sharp

Playing COI.... Using Inbreeding Coefficients

The Dark Side of Inbreeding


                                                     Example of a 7 Generation Biewer Pedigree