There are two copies of each gene, one from the mother, one from the father. That is the only actual hard and fast rule in genetics, since there could actually be 0 - 100% of the genes from each of the grandparents or beyond. On average, however, each grandparent would be assumed to contribute 25% of the genes. The Coefficient of Inbreeding, or COI, indicates the likelihood that both copies of any one of a dog's genes come from the same ancestor. The higher the value, the more times ancestors appear in both sides of the pedigree. Line breeding is done to help fix characteristics of breed type. Excessive line breeding, which would have a high COI, leads to inbreeding depression which is associated with a loss of genetic diversity: decreased lifespan, fertility issues, reduced litter sizes and birth weight, increased incidence of cancer and autoimmune diseases.

Berner-Garde has implemented calculation of the COI with a base year of 1966. What this means is that the calculation of COI for a dog uses all ancestors of that dog who were born in 1966 or later. This results in the COI calculations for all dogs going back to the same group of ancestors, providing a better estimate of the COI for use in comparing different possible matings than using a fixed number of generations. However, this method requires us to know the whelp date for each dog as that is what determines whether to include that dog or not.

Percent Blood is an estimate of the percentage of possible contribution of genes from any given ancestor.

To make our averages more meaningful when considering new breedings, the table below shows the average COI calculated for litters born in 2008 or later, calculated using the BG Base Year method. The average is shown for each number of complete generations along with the number of litters used to calculate those averages. Breeding for a COI of less than the breed average would be ideal. But as with any breeding selection, COI is just one aspect of the whole dog that can be taken into consideration. This also makes three numbers important, the COI, the total number of dogs in the evaluated pedigree, and the number of complete generations.

As you can see from the table, the COI typically is larger and more accurate with more complete generations. That is why it is very important to look at those other numbers when considering any specific COI value. Everyone can help make the pedigrees and COIs more complete by submitting data to fill in missing information.

To make getting a COI a bit quicker for Trial Pedigrees, there is now the option of selecting a fixed number of generations to use in the calculation. This also allows calculating a COI that will match with what your national Kennel Club may specify in its breeding guidelines. This method does not consider relationships beyond the number of generations used in the calculation, and whelp dates are irrelevant to the calculation. The ancestors in the oldest generation used for the calculation are assumed to be unrelated to each other. Therefore, this method will usually produce a lower COI than the Base Date method, and the COI will also be lower the fewer the generations used in the calculation. The Fixed Generation option is sometimes referred to as the Tabular Method. For more information on this method, go to: http://animalscience2.ucdavis.edu/ggg201d/references/tabular_method.html.

An important item to reiterate is that COIs calculated using a fixed number of generations do not need whelp dates like the base year method does. As a result, the number of complete generations could be different if you are looking at COI's calculated using different methods. Please remember, We can only compare different COI calculations with each other if we use the same method of calculation (Base Year or Tabular) and the same number of complete generations..