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BREEDING KNOWLEDGE · GENETICS
Inbreeding coefficient in dogs
The inbreeding coefficient, or COI, helps estimate relatedness mathematically within a planned mating. It is an important tool for me, but on its own it does not tell us whether a mating is good or bad.
Context is always crucial: I believe health, the population, natural hunting abilities, temperament, pedigree and the specific breeding goal must be considered together.
What the values can mean
The examples of relatedness are only theoretical guidance, assuming non-inbred founding animals and complete pedigree data.
0 %
No common ancestor was found within the pedigree analysed. This does not automatically mean that the animals are genomically unrelated.
≈ 3 %
A low but non-zero value. It can result from more distant or multiple relationships; without a complete pedigree, it cannot be used to determine a fixed degree of relatedness.
6.25 %
Under idealised assumptions, this corresponds to the expected COI of offspring from a mating between first cousins.
12.5 %
Under idealised assumptions, this roughly corresponds to the expected COI from half-sibling or grandparent–grandchild matings.
TWO DIFFERENT PERSPECTIVES
Understanding pedigree and genomic results
PEDIGREE-BASED CALCULATION
Pedigree COI
The pedigree-based COI depends on the quality and depth of the available ancestry data. A value calculated over five generations cannot be directly compared with one calculated over ten generations or the complete database. Missing ancestors can artificially lower the result.
DNA-BASED ASSESSMENT
Genomic inbreeding
DNA-based methods examine actual homozygosity or markers of relatedness. They answer a different question from a limited pedigree and can therefore produce different figures. The method and reference population must always be stated.
IMPORTANT CONTEXT
What the COI does not replace
- Health examinations and breed-specific genetic tests
- Assessment of temperament, function and hunting performance
- Consideration of the whole population and genetic diversity
- Awareness of frequently used breeding animals and the so-called popular sire effect
- Expert evaluation of a specific mating
OUR OWN CALCULATOR IS PLANNED
A reliable calculator needs good data
I intend to offer my own calculator only once the data source and calculation are truly reliable. It should clearly state the number of generations, data completeness, repeated ancestors, individual ancestors‘ COIs and the formula used.
01 · DATA
Inputs
- Complete parent and ancestor data
- Unique IDs rather than matching names alone
- Selected number of generations
- Known COI of common ancestors
02 · RESULT
Output
- COI as a percentage
- List of common ancestors
- Each ancestor’s contribution to the result
- Information about data completeness
Frequently asked questions
Does a low COI automatically mean a good mating?
No. A low value may support genetic diversity, but says nothing about health, temperament, performance, compatibility or specific inherited traits.
Why do calculators differ?
They may use different numbers of generations, databases, algorithms or DNA methods. Comparisons are only meaningful when the method and underlying data are identical.
What figure is “safe”?
There is no universal single threshold that automatically makes a mating safe or unsafe. The aim is to keep additional inbreeding as low as possible and to assess the value in the context of the breed population, health and the overall breeding goal.
Sources and further reading: Royal Kennel Club: Inbreeding calculators as well as the UC Davis Veterinary Genetics Laboratory. These examples provide context and do not replace expert breeding advice.
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