Inbreeding, put simply, is the mating of related individuals. High levels of inbreeding can impact the health of individual dogs, as it could increase the chances of a dog being at risk for both known and unknown inherited disorders. It will also have an impact on the breed as a whole, for example, a reduction in litter size and fertility.

It is impossible to make precise predictions about the exact impact that inbreeding has on an individual dog, but we do know that, as the degree of inbreeding increases, the risk of having a serious and harmful impact on the breed as a whole will increase.

How can you measure the degree of inbreeding?

The degree of inbreeding can be measured by using an Inbreeding Coefficient, or Coefficient of Inbreeding (COI). This is the probability that two copies of the same gene have been inherited from an ancestor common to both the sire and dam. The lower the degree of inbreeding, the lower the inbreeding coefficient.

Inbreeding Coefficient Calculators

The Kennel Club's free online health resource, Mate Select, provides breeders with inbreeding coefficient calculators for all dogs found on the Kennel Club's Breed Register. These calculators use all pedigree records stored on the Kennel Club's database to calculate the result, for:

  • Puppies thatcould beproduced from hypothetical matings, allowing you to make informed decisions before choosing a breeding pair 
  • An Individual Kennel Club registered dog
  • Each breed

Use any of our inbreeding coefficient calculators here.

Each of these COI calculators use all available pedigree information and does not limit the number of generations used, making each calculation as precise as possible.   The number of generations available for individual calculations is provided on the right hand corner on Mate Select.

Putting your COI result into perspective

The COI calculator provides you with a percentage score; the lower the percentage, the lower the degree of inbreeding.

Therefore, an inbreeding coefficient of:

  • 0% indicates a dog that comes from two unrelated parents, based on all available pedigree information
  • 12.5% would equate to the genetic equivalent of a dog produced from a grandfather to granddaughter mating
  • 25% would equate to the genetic equivalent of a dog produced from a father to daughter mating.

Inbreeding can be accumulative, so if it has occurred to a significant degree over several generations, the inbreeding coefficient may exceed 25%.

Using the COI to help make breeding decisions

When choosing a potential mate for your dog, the Kennel Club recommend that breeders use Mate Select to calculate the inbreeding coefficient of the puppies that could be produced from a hypothetical mating.

The current Kennel Club breeding guidelines are that, where possible, breeders should produce puppies with an inbreeding coefficient which is at, or below, the annual breed average and ideally as low as possible. The annual breed average is recalculated each year and is shown to you each time you use the COI calculators.

Breeders should be aware that the inbreeding coefficient is a measurement of risk and does not guarantee that puppies produced will, or will not, have any inherited health conditions. There are other equally important factors to consider when deciding whether two dogs should be mated together, such as temperament, available health test results, the general health of the dogs etc. Your decision should be well balanced between the inbreeding coefficient and the good qualities of the sire/dam that you are considering.

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Will the Kennel Club still register puppies with a higher than average inbreeding coefficient?

The Kennel Club will still register the puppies of a mating which results in an inbreeding coefficient which is higher than the annual breed average, but it is recommended that you consider a different pairing, all other considerations being equal. If you do go ahead with the mating and plan to use any of the puppies for breeding in the future, it is strongly recommended that you take extra care to choose a highly unrelated mate that will result in puppies with an inbreeding coefficient well below the breed average.

To help reduce the highest degrees of inbreeding, the Kennel Club does however not register puppies produced from a mating between father and daughter, mother and son, or brother and sister, save in rare exceptional circumstances for scientifically proven welfare reasons.

For further information on other health considerations to make prior to breeding, please see our 'Breeding for Health' information guide.

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