COI & ALC: Understanding Genetic Diversity in Pointer Breeding

The Coefficient of Inbreeding (COI) and Ancestor Loss Coefficient (ALC) are internationally recognised tools used by breeders, geneticists, and kennel clubs to understand genetic diversity within a population. At Ledgands, these calculations draw on more than 200 years of Pointer history, offering one of the most complete views of the breed’s genetic landscape anywhere in the world.

What COI Tells Us

COI estimates how closely related the sire and dam are by measuring the probability that a dog inherits identical copies of a gene from a shared ancestor. A higher COI indicates a narrower genetic base, while a lower COI reflects greater diversity.

COI helps breeders understand the potential impact of a mating on health, fertility, immune strength, and long‑term sustainability. It does not predict specific diseases, but it does highlight the overall level of genetic concentration within a pedigree.

To give the numbers context:

  • ~25% is equivalent to a full‑sibling mating
  • ~12.5% to a half‑sibling mating
  • ~6.25% to first cousins

These comparisons help breeders interpret the figures without prescribing what is “good” or “bad.”

It is a mathematically computed percentage that describes the degree to which two animals are inbred, meaning that one or more ancestors appear more than once in the pedigree. The theory is that a higher degree of inbreeding results in expression of undesirable recessive gene defects in the offspring. Some people believe that 0% inbreeding, or at least a very low number, is preferable. Sometimes in the literature, you may see COI abbreviated as IC.

Also see: https://en.wikipedia.org/wiki/Coefficient_of_relationship

What ALC Reveals

ALC measures how many unique ancestors appear in a pedigree. Where COI looks at the degree of inbreeding, ALC looks at the breadth of the ancestral base.

A low ALC suggests repeated ancestors and potential bottlenecks; a high ALC indicates a wider, more diverse foundation. This makes ALC especially useful for identifying hidden patterns that COI alone may not show.

The Ancestor Loss is a good indication for the amount of linebreeding and inbreeding or the degree of kinship of a certain dog. The Ancestor Loss is calculated by comparing the number of ancestors that were possible in that pedigree with the actual number of different ancestors. It describes the degree to which recessive traits from ancestor generations are lost. Another way to think of it is as how many unique ancestors an animal has. If there are no duplicate ancestors, then no unique ancestors are “lost”, and the ALC = 0%. When there are duplicate ancestors, more and more unique ancestors are “lost”, and the ALC percentage goes up. A lower number is preferable. Sometimes in the literature, you may see ALC abbreviated as AVK, which stands for the German word AhnenVerlustKoeffizient.

Using COI and ALC Together

Viewed together, COI and ALC offer a balanced picture of genetic diversity. A mating may have a modest COI but still show a low ALC if the same ancestors appear repeatedly across generations. Conversely, a pairing with a slightly higher COI may still maintain a broad ancestral base.

Neither number should be used in isolation. Instead, they help breeders understand the structure of a pedigree, compare potential pairings, and make decisions that support the long‑term health and resilience of the breed.

How Calculations Work

COI and ALC values depend on the depth and completeness of the pedigree. Because the Ledgands database contains extensive historical data, calculations often reach far deeper than standard five‑generation pedigrees. As new dogs and historical lines are added, values may update to reflect improved information.

Frequently asked questions [FAQ]

Click on the plus [+] sign to open each FAQ response.

There is no universal “correct” COI. Lower values generally indicate greater diversity, but breeding decisions should consider type, health, temperament, and long‑term goals. COI is a tool, not a rule.

As new dogs and historical pedigrees are added to the database, the system gains more information about shared ancestors. This can increase or decrease COI depending on the depth of the new data.

COI measures probability, not the specific genes inherited. Two dogs may share the same COI but have very different ancestors, or one may have a single ancestor repeated many times while the other has several ancestors repeated once.

Not necessarily. A low COI indicates diversity, but breeders must also consider structure, health, temperament, and breed type. COI is one part of a balanced breeding strategy.

ALC shows how many unique ancestors appear in a pedigree. A dog may have a low COI but still come from a narrow gene pool if the same ancestors appear repeatedly across generations. ALC reveals this hidden structure.

COI and ALC are calculated using the full depth of the database — often far beyond the standard five‑generation pedigree — providing a more accurate and historically informed result.

No. COI does not identify specific diseases. It reflects overall genetic concentration, which can influence health trends but does not replace health testing or veterinary screening.

Not automatically. Linebreeding can consolidate desirable traits when used carefully and with full awareness of genetic risks. COI helps breeders understand the level of concentration involved.

This means no shared ancestors were found within the calculated range. It does not guarantee absolute unrelatedness — only that no common ancestors appear in the available pedigree data.

What Is COI?

The Coefficient of Inbreeding (COI) is a number that shows how closely related the sire and dam are. If they share ancestors, the COI will be higher. If they have few or no shared ancestors, the COI will be lower.

A higher COI means the genes in the litter are more similar. A lower COI means there is more genetic variety.

COI does not predict specific health issues, but it helps breeders understand the overall level of genetic concentration in a pedigree.

What Is ALC?

The Ancestor Loss Coefficient (ALC) shows how many unique ancestors appear in a dog’s pedigree.

  • A high ALC means many different ancestors contributed.
  • A low ALC means the same ancestors appear repeatedly.

ALC helps breeders see how broad or narrow the genetic base is behind a dog or planned mating.

Why These Numbers Matter

COI and ALC are simple tools that help breeders:

  • understand genetic diversity
  • avoid unnecessary inbreeding
  • preserve a wide, healthy ancestral base
  • make informed, responsible breeding decisions

They are not rules — just helpful indicators that support long‑term breed health.

How the Database Calculates Them

The Ledgands system uses the full depth of the pedigree database — often far beyond the usual five generations — to give the most accurate COI and ALC values possible. As more historical dogs are added, these numbers may update automatically.

In Summary

  • COI shows how closely related the parents are
  • ALC shows how many unique ancestors appear
  • Together, they give a simple picture of genetic diversity

These tools are part of responsible breeding, alongside health testing, temperament, structure, and knowledge of the breed.

COI & ALC for advanced breeders

This section provides a deeper look at how COI & ALC function within population genetics and how they can be applied to long‑term breeding strategies.

Calculation depth and pedigree completeness

COI accuracy increases with the number of generations included. A five‑generation pedigree contains 62 theoretical ancestors, but deeper pedigrees – such as those used in the Ledgands Pointer database — may include hundreds or even thousands of individuals. This depth allows the algorithm to detect:

  • historical bottlenecks
  • founder effects
  • repeated ancestors many generations back
  • long‑term patterns of linebreeding

Missing ancestors reduce accuracy by artificially lowering COI and inflating ALC. As the database expands, both values become more precise.

Inbreeding Pathways and Common Ancestors

COI is influenced not only by how many ancestors are shared, but by how often they appear and how recently they occur. A single ancestor repeated multiple times across a pedigree can have a greater impact than several unique shared ancestors.

This is why two matings with identical COI values may differ significantly in genetic structure – and why ALC is essential for interpretation.

ALC as a Measure of Genetic Drift

ALC quantifies the loss of unique ancestors across generations. Low ALC values indicate that the same individuals appear repeatedly, often due to:

  • over‑use of popular sires
  • closed gene pools
  • historical bottlenecks
  • limited founder populations

Tracking ALC over time helps breeders monitor genetic drift and avoid the gradual narrowing of diversity that can occur even when COI appears moderate.

COI × ALC Interaction

The most informative view comes from examining COI & ALC together:

  • High COI + Low ALC Indicates strong inbreeding pressure and a narrow ancestral base.
  • Low COI + Low ALC Suggests a broad mating but a historically restricted gene pool.
  • Low COI + High ALC Represents the most diverse scenario, with both low relatedness and many unique ancestors.
  • High COI + High ALC Rare, but may occur when two genetically diverse individuals share a single influential ancestor.

Understanding these patterns helps breeders maintain type while safeguarding long‑term genetic health.

Effective Population Size (Ne)

Although not directly calculated here, COI & ALC both relate to effective population size, a key measure in conservation genetics. High COI and low ALC typically indicate a shrinking Ne, which increases the risk of:

  • loss of genetic variation
  • accumulation of deleterious alleles
  • reduced adaptability

Monitoring COI and ALC helps breeders contribute to a healthier, more sustainable population.

This page was last updated on Saturday 7th February 2026