RESPONSIBLE BREEDING
COI, relatedness and linebreeding
What the pedigree estimates, coverage, recommendations and limitations.
30 SECONDS · In a nutshell
Pedigree COI estimates genetic relatedness from known ancestry. It helps compare matings; it does not diagnose health.
UNDERSTANDING RELATEDNESS
An ancestor can appear in both branches
3 MINUTES → EXPERT · Explanation and sources; open the sections to explore further
Pedigree and diversity
Pedigree COI: understanding relatedness
A percentage to help understand a pairing. Its value depends on the known ancestors and should be accompanied by its source, depth and coverage.
What COI means
COI stands for coefficient of inbreeding. Calculated from the pedigree, it estimates the probability that the two copies of a gene —one inherited from the father and one from the mother— are identical by descent: they originate from the same ancestral copy. The COI of a pairing refers to its expected offspring.
A COI of 6.25% does not mean that 6.25% of the puppies will become ill. It is a pedigree estimate, not a diagnosis or a direct measurement of DNA. Royal Kennel Club · definition and limitations.
Individual pedigree COI
A dog’s inbreeding, explained through its pedigree
The individual pedigree coefficient of inbreeding estimates the probability that a dog’s two copies of a gene descend from the same ancestral copy, inherited through its sire and dam. It is calculated by identifying ancestors shared by both sides of the pedigree.
An individual COI describes the parental relatedness that produced that dog. A mating COI estimates inbreeding in future puppies and requires comparing both parents’ pedigrees: it is not the average of their individual COIs.
What value is recommended for an Aussie?
ASHGI recommends knowing the COI over ten generations and aiming below 10%, while reducing the COI of future litters. This is breeding guidance, not a universal approval threshold. Our partial examples cannot be compared directly with a reference calculated over ten generations.
Pedigree COI is distinct from heterozygosity and genomic COI measured from DNA. A low value does not guarantee health or approve a mating; health screening and family history must also be considered.
ASHGI · breeding recommendations · ASHGI · pedigree depth and COI
What it is used for
It helps compare pairings, identify shared ancestors and reduce the concentration of a single line. Inbreeding may increase the chance of recessive variants coming together and contribute to fertility and vitality problems. The aim is to preserve diversity and welfare; the FCI recommends avoiding heavy inbreeding and excessive use of the same breeding dog. FCI · International Breeding Strategies, section 3.
Is there an acceptable percentage?
There is no universal number that makes a pairing safe. Organisations distinguish selection recommendations from the conditions for registering a litter.
Breeding recommendations
The Royal Kennel Club advises aiming for a COI as low as possible and, where feasible, at or below the breed average. Its calculator uses all available pedigree information; that average should not be compared directly with a partial calculation from another database. Read the recommendation.
The Swedish kennel club SKK uses 6.25%, the theoretical equivalent of first cousins, as an upper reference that should not be exceeded, rather than a target. This is guidance from that organisation, not a universal limit or a guarantee of health. SKK · interpretation of its breeding rules.
Registration conditions in Spain
The RSCE litter registration information prohibits mother–son, father–daughter and full sibling pairings; it allows half sibling pairings. Registration eligibility is not a health or diversity recommendation. The page consulted does not specify a general maximum COI. RSCE · litter notification and registration.
Why some relatedness is considered
Lines within a breed share ancestors. Excluding too many breeding dogs through rigid requirements can reduce the available diversity; the FCI warns about this effect. Selection must balance diversity, health and realistic alternatives, aiming to reduce relatedness without concentrating breeding in a few dogs. This explains the gradual approach; it does not justify every pairing. FCI · introduction and section 3.
| Expected COI | Illustrative pairing |
|---|---|
| 6.25% | First cousins |
| 12.5% | Half siblings or grandfather–granddaughter |
| 25% | Full siblings or father–daughter |
Simplified examples: no prior inbreeding or other relationships among the founding ancestors. Additional shared ancestry can change the result. The table explains magnitudes; it does not authorise pairings. Sources: SKK and Royal Kennel Club.
Linebreeding: why it is used and how it affects COI
Linebreeding aims to maintain the influence of one or more ancestors by mating related dogs. Breeders use it to try to preserve family characteristics, such as breed type or working abilities. This is a selection aim, not a guarantee that those traits will be inherited.
Genetically, it is a form of inbreeding, even though breeding terminology distinguishes it from matings between very close relatives. Shared ancestors can increase the expected COI compared with a less related pairing. No fixed percentage defines linebreeding: all paths, previous inbreeding and pedigree depth matter.
Concentrating a line can also bring together harmful variants and reduce diversity. A higher COI does not by itself prove that puppies will become ill, but neither does it demonstrate quality or justify a mating. Available tests do not rule out every hereditary risk.
To assess a project, consider the breeder’s stated selection aim alongside the COI, pedigree coverage, shared ancestors, health screening and family history. Available alternatives should also be compared. The FCI recommends avoiding heavy inbreeding and preserving genetic diversity; the cited document does not declare all linebreeding wrong or reject every mating with shared ancestors. Assessment depends on the specific pairing, not just the name of the strategy.
Sources take different approaches. The scientific report commissioned by the RSPCA highlights the risks of concentrating a line. For Australian Shepherds, ASHGI provides breed-specific resources on COI and breeding strategies. These references help explain and assess the practice; they do not constitute general approval of matings or certification of Lunamar.
RSPCA · Rooney & Sargan (2009), §4.1–4.2 · Royal Kennel Club · COI · FCI · International Breeding Strategies, §3 · ASHGI · Playing COI
How to read it on Lunamar and in reports
- Value, method and date. Check which version of the pedigree was used.
- Depth and coverage. Our relatedness panel examines five generations of ancestors for each parent: 124 positions in total. Coverage of 40/124 means that 40 positions are known; it is not a percentage of health or DNA diversity.
- Ancestors and paths. Parents = generation 1 for each selected parent, grandparents = 2 and great-grandparents = 3. An occurrence at generation 3/3 indicates a great-grandparent shared by both. Multiple paths must not be added together without applying the calculation method.
- Missing information. A result of 0% with incomplete branches only reflects what that pedigree can detect. Adding further ancestors can change the result.
- The full decision. COI does not replace inherited disease testing, clinical assessments, family history or temperament assessment.
Pedigree COI and genomic COI measured from DNA use different approaches. They should not be interchanged or compared as if they were the same calculation. SKK · genetic diversity and genomic inbreeding.
A report records the information available on its date. The percentage informs the review of the pairing; it does not automatically approve it.
From the guide to your Lunamar records
The library explains breed and health concepts. The private platform organises dogs and kennels, preserves evidence, explores pedigrees and records reproduction. Reading a guide does not create records, grant access or confirm a result.
Private management supports pedigree imports, review of proposed ancestors, and individual or mating COI. Accept only relationships supported by evidence. Check the current method, coverage, depth and calculation date. Dated example tables in this library are historical snapshots and do not update automatically when a profile changes.
Reproductive tracking distinguishes scheduled dates, performed procedures, confirmed pregnancy and birth. Incoming email requires review and does not complete these milestones by itself. Private closure and its publication require separate steps.
For an individual dog, discuss tests and family history with the veterinarian. The system does not diagnose or decide treatment, ovulation or insemination timing. Missing data must remain identified as pending information.
Open the private platform user guides
Application to Lunamar features reviewed on 22 October 2026. Each reading retains the scope of its clinical sources and review dates.