If you were to talk about the importance of genetics in the breeding of pedigree dogs, there is no way we can exclude the term COI or coefficient of inbreeding! This mathematical sounding term refers to the formula or equation regularly used for determination of the number of common ancestors existing between any two dogs, and the amount of similarity between them on the genetic level. It functions as an important tool for all the dog breeders out there, as it enables them to decide whether or not should they breed any two dogs, and provides them with a fair idea about the possible results too.


How genetics matter?

When two dogs have the same genetics, implying that they are closely related, it can have both bad and good effects. After all, it’s the genetic similarity only which gives any pedigree dog his/her pedigree status. Dogs belonging to the same breed should ideally have the same traits, meaning the same genetic similarities. But if two dogs have excessive genetic similarities or are very closely related, it can also lead to the introduction of certain undesirable traits into the gene pool, for instance hereditary and genetic health problems, strengthened by such selective inbreeding.

Delving deeper into the canine genetics

Any given dog has close to 20,000 or more genes in him/her, majority of which are fixed, implying that all the dogs belonging to the same breed have two copies of same genes – one inherited from the dam and the other from sire. Some genes may not be fixed, for instance the ones corresponding to the color wherein there is possibility of more than one color, for instance, the possibility of black, chocolate and yellow colors in the Labrador retriever breed.
Genes normally exist in pairs and every pair of genes is referred to as allele. If a pair has two identical genes, they are referred to as homozygous genes. If the two genes are not identical, they are referred to as heterozygous.
If there are more homozygous genes at the time of breeding pedigree dogs, there will be less diversity than the present. On the other hand, the presence of more heterozygous genes will lead to more diversity. Mind you, there is nothing wrong in genetic diversity! In fact, it’s a good thing and critical too, when it comes to the health and wellness of the offspring! However, a certain level of sameness is needed when it comes to pedigree dog breeds, in order to retain their particular bloodline. How else will they be known as pedigree dogs otherwise?!

Enters the coefficient of inbreeding or COI!

COI or coefficient of inbreeding is actually a statistical equation that shows the genetic similarity between the puppies produced from any crossbreeding. It’s depicted in the form of a percentage of the known crossing. To give you an example, if you take two completely unrelated dogs belonging to the same breed and have them crossed, followed by allowing their offspring couple to mate (mating of a brother and sister), the resulting puppies will statistically have a COI of 25%. Simply put, there’s a 25% probability that any given allele of the puppies would have identical genes, owing to common ancestors. This 25% probability is over and above the natural sameness that exists between dogs of the same breed.

Some of the most commonly known inbreeding crosses within the pedigree dogs, along with their corresponding COIs are:
Brother – sister: 25%
Mother – son: 25%
Father – daughter: 25%
Grandparent – grandchild: 12.5%
Half-sister – half-brother: 12.5%
Great-grandparent – great-grandchild: 6.25%
First cousin – first cousin: 6.25%

Please keep in mind that COI is only a statistical equation, implying that it provides only an average figure and is by no means a direct reflection of any dog’s reality. There’s always a chance of some variance when it comes to the percentage levels in any given dog. However, statistical figures are normally considered insightful and often accurate enough to be proved sufficient.

Tracking of the historical family tree

Apart from paying heed to the immediate ancestors of any dog, the COI tracks the ancestry of a dog back to 5, 10 or sometimes even more number of generations. In case of some pedigree dog breeds which have comparatively smaller gene pools, and also in case of some formative and new breeds, the dogs of that breed are usually in great demand. This implies that the same few names may come up every time when it’s about ancestral mating within any given dog’s family tree. Although this helps in fixing some desirable traits that are present in only that breed, it can also sometimes lead to problems too.

When should you be concerned about genetics and why?

As also mentioned earlier, dog breeders need to do a sort of balancing act as far as the canine genetics are concerned, specifically in cases wherein they need to fix some uniform desirable traits that are a characteristic of that particular breed, without bringing any hereditary health defects and genetic anomalies into the equation.
Almost every dog breed present in this world has been subjected to inbreeding at some point of time in its history. In fact it is considered necessary in establishment of some newer and smaller breeds. Nevertheless, no matter how carefully such inbreeding is managed for avoiding the possible defects and problems, it always inevitably results in certain subtle problems over the course of time.
Inbred dogs generally have smaller litters, which are also weak and more likely to face early illnesses. Inbreeding may also lead to certain immunity and fertility-related problems.
Generally, a COI of over 6.25% is termed undesirable within the reputed and well-known pedigree dog breeds. This is because there are high chances of certain subtle problems entering the gene pool above this level. Agreed that inbreeding is almost unavoidable when it comes to development and establishment of a certain breed, dogs that have a COI higher than 25% have considerably shorter lifespans and poor health than the majority of genetically robust dogs.


It’s important to remember that COI is just a statistical analysis and is not the actual assessment of the genetics of any given dog. There is no guarantee that having a low COI percentage would lead to better health and a high COI percentage would result in great health problems. Nevertheless, all potential dog owners and breeders must consider the odds and the possible health implications on their dogs before they opt for breeding pedigree dogs with high COI.
To sum up, genetics have a very important role to play in breeding of pedigree dogs.