COEFFICIENT OF INBREEDING – COI
In their quest to produce happy, healthy puppies, many breeders run genetic reports, or pedigree analysis on a potential breeding, looking for both pitfalls and strengths. These reports give us a lot of data- but what exactly are these numbers, what information do they give us, and how should they be used?
The pedigree database on the site, shows the COI, or Coefficient Of Inbreeding, for each dog when you bring up a pedigree. This is also sometimes referred to as IC, Inbreeding Coefficient. It does this automatically and is not something that I have set it to do. The database uses Wright’s Inbreeding Coefficient Program to calculate the COI for each dog, being set at default to calculate this over 10 generations. It can calculate the COI for each dog using anything up to 60 generations. The Inbreeding Coefficient is expressed as a percentage. The more common ancestors there are in a pedigree and the closer they are in terms of generations to their descendant, then the higher the Inbreeding Coefficient of that descendant will be.
The KC’s recently launched Breed Mate Select web site does the same thing and uses the same program, but does not state how many generations are used to calculate the COI. There are several different programs available for calculating the Coefficient Of Inbreeding, but the Wright’s program is widely considered to be the most accurate.
Whilst most breeders recognize that a mating between half siblings, or cousins, represents inbreeding, not everyone understands which one is the closest relationship. The standard definition of ‘Inbreeding’ is that it is any scheme which results in the sire and the dam having common ancestors. The parameter used to express this common heritage, is called the INBREEDING COEFFICIENT and was first proposed by Sewell Wright in 1922. Designated ‘F’ by Wright, but more commonly known as ‘IC’, or ‘COI’ by breeders. It can theoretically range from 0 to 100% but as a general rule, the lower the number, the less inbreeding there is.
When looking at the same dog’s COI on different web sites, there can often be differences in the results. This is due to missing ancestors in the pedigree. However many generations are used to calculate the COI of a dog, each of the generations in the pedigree, needs to be 100%. If the ancestors are not 100% present for each generation, then this will ultimately affect the end result. Put simply, to calculate the COI and receive an accurate result, there should not be any missing ancestors in the pedigree. Once the missing ancestors are added, the result will go up or down accordingly.
When using a pedigree database, the COI% for that dog can often be seen, but this is only part of a Pedigree Analysis. When breeders ask for a Pedigree Analysis, or Genetic Report for a particular dog, or planned litter, they are given other information as well.
PEDIGREE ANALYSIS DECIPHERED by Tina Porter, explains the information contained in such a report.
The following table is a sample pedigree report for the hypothetical mating between:
Lakeways Its Yours Truly Sierra (Tru) & Lakeways Take A Chance On Me (Joss)
The top line: TEST:: Tru/Joss:: 091707 is the data for the hypothetical puppy
|Name||COI||COR||Count||Min Gen||Max Gen||% of Blood||Cov AX|
|#TEST :: Tru/Joss :: 091707||9.70%||100%||1||0||0||0%||109.70%|
|Lakeways Its Yours Truly Sierra||0.03%||57.01%||1||1||1||50%||59.72%|
|Lakeway’s Take a Chance on Me||13.61%||59.57%||1||1||1||50%||66.50%|
|Lakeways It’s Simply Simon-Zion||14.97%||42.08%||1||2||2||25%||47.26%|
|Lakeway’s Bailey Lady of Zion||16.69%||38.59%||1||2||2||25%||43.67%|
|Twincedars Desparado – OTX||0%||23.92%||1||2||2||25%||25.05%|
|Indy Woods of Sierra||11.51%||42.73%||1||2||2||25%||47.25%|
|Shiloh’s Wolfin Sasquach||3.77%||34.05%||8||4||7||24.22%||36.33%|
|Crane’s Our-Tribute-To Contessa||11.23%||32.31%||2||3||4||18.75%||35.69%|
|Jnk Smoke’N Black Bear Of Zion||10.83%||33.18%||2||3||4||18.75%||36.58%|
|Shiloh’s Easy Rider||3.91%||21.80%||12||5||8||15.63%||23.27%|
|Morris Good Morning Mona||0%||24.48%||9||5||8||13.67%||25.64%|
|Snow’s A Tribute To Pax-Zion||7.90%||28.33%||1||3||3||12.50%||30.82%|
|Sierra’s Close Encounter||16.25%||28.08%||1||3||3||12.50%||31.72%|
|Twin Cedar’s Northern Dancer||0%||12.02%||1||3||3||12.50%||12.59%|
|Twincedars Adorable Adelaide||0%||11.95%||1||3||3||12.50%||12.51%|
|Shenandoah’s The Phantom V Zion||14.97%||37.13%||1||3||3||12.50%||41.70%|
|Super Sweet Sabrina Selah||26.34%||13.21%||12||5||9||12.30%||15.55%|
|Shiloh’s Kara Lobo Of Emmview||2.15%||15.69%||18||6||11||10.94%||16.60%|
The following explains the content of such a report.
COI – INBREEDING COEFFICIENT, OR IC
- A number created by calculating how many times (and in what generation) shared ancestors appear in a pedigree of a specific dog.
- The higher the number, the more ancestors a pup’s Sire and Dam have in common. COI’s are 0% for dogs with no common ancestors.
- The number also tells you the probability that both alleles for any given gene come from the same ancestor. (This is called having a homozygous genotype.)
- The higher the number, the greater the chance of locking in a trait – either good or bad.
- The higher the number, the more you risk the effects of inbreeding.
- Any trait your dog is homozygous for, it will pass that allele on to its pups.
KEEP IN MIND
- This number doesn’t tell you which ancestor is contributing the alleles that are being doubled on. Is it the one on the dam’s side that produced the problem, or the fabulous great-great- grandsire who lived to be 16?
- COI doesn’t tell you which particular alleles you might be doubling up on. Is it a “good” allele for a trait, which you want the dog to have? Or is it a “bad” allele that causes disease and structural faults?
- Due to events during sperm and egg cells production, the COI is only a “guesstimate”. (A guide). The reality is, it could be higher or lower than this number, depending upon which specific alleles are inherited by each dog in the pedigree from the common ancestor.
COR – RELATIONSHIP COEFFICIENT, OR RC
- An approximate percent of the genes passed down from a specific ancestor to the dog whose pedigree you are studying.
- The higher the COR value, the more genes the ancestor and hypothetical pup will have in common, and the greater the chance they will share a trait.
- COR values are influenced by the dog’s COI number, presence of other relatives in the pedigree, and pedigree position.
KEEP IN MIND
- Again, this is only an approximate percentage of the genes. When the dam “passes” her genes to the puppy the COR expects that 50% are coming from her dam and 50% from her sire. But this may not be the case. Of the genes the dam passes to the pup, anywhere between 0 and 100% of them may come from her dam, not just 50%. This is why siblings don’t all look alike (and are genetically different) – they are getting different combinations of genes from their parents.
- The number of times this individual shows in the pedigree. Higher the count, the higher the possibility of locking in traits from this ancestor.
KEEP IN MIND
- While this number can be quite large and the ancestor’s genes are found in the dogs we are breeding, it is more important to look at his COR and Cov AX numbers to determine his true genetic influence. If for instance, this dog first appears in the 8th generation, and his genes have been filtered through his offspring to our current breeding pair, it is the genes being held by the dogs in the first 4 generations and their immediate relatives that are more likely to be of worry.
- The first generation where the dog appears in the pedigree. The lower the generation number, the more recent the dog. The 1st generation are the parents, 2nd generation are the grandparents etc.
- The last generation where the dog appears in the pedigree.
% OF BLOOD
- Another method of showing the possible genetic contribution of each ancestor.
- Based on the calculation that each dog passes 50% of its genes on to the next generation. So for the planned puppy – the parents each contribute 50%, the grandparents contribute 25%, the great grandparents contribute 12.5% and the great-great grandparents contribute 6.25%, etc.
- Dogs that appear more than once in the pedigree will have % of Blood number that doesn’t follow this pattern. Their contribution from each appearance in the pedigree is combined into one number.
KEEP IN MIND
- This is different from RC (Relationship Coefficient) in that the calculation for RC uses the IC (Inbreeding Coefficient) for the dogs. % of Blood is based only on the dog’s position in the pedigree.
- Problems with this data are the same as the ones for RC (Relationship Coefficient).
COV AX –GENETIC COVARIANCE
- It determines the extent to which the planned puppies will resemble that specific ancestor.
- COR, (Relationship Coefficient) COI (Coefficient of Inbreeding) and % of Blood are used to calculate genetic covariance. The more homozygous the dogs genes (COI), the more of that dogs genes get passed on to its offspring (COR), and the closer that dog appears in the pedigree (Min Gen), the more of its genes the puppies will carry (% of Blood), therefore, it is more likely its offspring are going to look like that dog.
KEEP IN MIND
It is only as accurate as the numbers used to create it – so the “Keep in minds” are also true for this one. If the stud looks like his great grandpa on the sire’s side, that great-grandpa may be a greater influence than the numbers suggest.
Each of these numbers can give useful information when planning a litter. While it would be nice to think that there could be a magical formula, or combination of COI, COR & CovAX numbers that would create the perfect litter of puppies, it simply is not true. An IC (Inbreeding Coefficient) of less than 10% will not guarantee you a healthy litter, just like an IC of over 30% does not mean all the puppies will be sickly. Instead, these numbers are best used to help us to identify important individuals (those who will make a large genetic contribution to our puppies). Then it is up to the breeders to research those individuals, find the plusses and minuses associated with them, and then make the best decision possible.
The most useful COI number is the one for the planned puppy. Having a low COI lessens the risk of doubling on a nasty hidden recessive allele, suffering from inbreeding depression; helping to keep the gene pool healthy. The COI’s for the rest of the dogs in the pedigree are interesting, but only useful in that they are used to calculate COR and CovAX.
COR, % OF BLOOD, COUNT & COVAX
Are all are excellent for pointing out dogs in the pedigree that we should know more about. The higher these numbers are, the more genes they will give to the puppies, the more they will determine what your puppies will look like, therefore the more important they are to investigate. This is why it’s important to also look at the ancestors (and their littermates), especially the 2nd and 3rd generation, so you can see some of the traits they have and get an idea of some of the genes they carry.
QUESTIONS RAISED BY THIS SHOULD BE:
What are some of the health issues associated with:
- This dog?
- This dog’s siblings?
- This dog’s offspring?
- This dog’s ancestors?
Pedigree report numbers do not tell you what they look like, what they act like, or how healthy they were.
Pedigree Analysis Reports are valuable tools that can help give us a sense of which dogs in the pedigree will be the largest genetic contributors to a litter. Once those individuals are identified, they can be researched further to get a sense of which genes they do carry. However, it is not the only tool a breeder should rely upon. These numbers alone do not give enough information about the dogs to be the sole basis for planning a litter. Breeders must always take into account the actual dogs that are being considered for breeding. In addition to their individual health, temperament and structure, breeders must also attempt to learn as much information as possible about their siblings and parents.
Coefficient of Inbreeding, or COI, as it is more commonly known, is just a way of determining the level of inbreeding for the chosen dog. Whilst it seems to be the latest buzz word on the Internet, amongst those interested in dog breeding, it should be remembered that it is only one of many useful tools to help the breeder produce a healthy litter, in the same way that Hip Scores and DNA test results are useful. Obviously when breeding a litter, or planning a litter, all other aspects should be taken into consideration. The COI should be seen in context with everything else and not used as the only deciding factor. Bear in mind that it is perfectly possible for a dog with a high COI to not have, or to not produce health problems and equally it is perfectly possible for a dog with a low COI to have, or to produce health problems. It is after all just another useful tool for the breeder.