What is the Coefficient of Inbreeding (COI)? The short-version is how closely related an offspring's parents are. Too high of a COI results in negative outcomes for the offspring, and the breed.
The scientific answer according to Science Direct is, "The coefficient of inbreeding (F) for a child of a consanguineous marriage is the probability that the child receives two alleles at a given locus that are both from the same ancestor and are, thus, identical by descent (autozygous)."
So why does this matter? The higher the COI, the more homozygous an animal's genes would be. Once the COI reaches certain levels, one will begin to see deleterious effects of inbreeding, resulting in loss of vitality in the offspring, smaller litters, higher mortality, and increased genetic defects and mutations (WHS, for example).
At what level COI do you begin to see these effects? One will begin to see the negative effects of inbreeding at a COI around 5%. Once the COI reaches 10% or higher, these deleterious effects reach the threshold of the "extinction vortex." As stated by the Institute of Canine Biology, "[t]he combined effects of these make 10% the threshold of the 'extinction vortex' - the level of inbreeding at which smaller litters, higher mortality, and expression of genetic defects have a negative effect on the size of the population, and as the population gets smaller the rate of inbreeding goes up, resulting in a negative feedback loop that eventually drives a population to extinction."
How do you calculate the Coefficient of Inbreeding (COI)? As you might expect, the Coefficient of Inbreeding can be calculated with a mathematical formula. "In general, for autosomal loci, the inbreeding coefficient for an individual is F = (½)(n1+n2+1), where n1 and n2 are the numbers of generations separating the individuals in the consanguineous mating from their common ancestor. (This formula assumes that the common ancestor is not inbred.)" - Science Direct
Babydoll Southdown Sheep Breeders Association has a helpful table (see below) with simple examples of inbreeding coefficients.
That formula is too much, is there an easier way? Fortunately NABBSSAR.org has a phenomenal Coefficient of Inbreeding (COI) calculator, which can go up to 12 generations beyond the offspring you're calculating.
If you already use our free Google Sheets Pedigree Maker & COI Calculator, you can select the hedgehog you want to calculate the COI for on the 'Pedigree 8 GEN' tab, go to the 'Calculate COI' tab, copy the data highlighted, paste on the NABSSAR COI% Calculator website and calculate. Don't worry, more specific instructions are available in the Google Sheet.
The calculation of the Coefficient of Inbreeding is only as good as the data you put in. The more expansive your data, the better the calculation. Also, most calculators assume the ancestors are not inbred themselves. In the event the ancestors are inbred, the coefficients will actually be higher than what is displayed.
Note: I am not a biologist. I just care about the quality and outcomes of our hedgehogs. This is information I have gathered from resources listed below. What information would you add about the Coefficient of Inbreeding? Let me know!
Rachel, the owner of Penny's Prickly Pigs has been breeding hedgehogs since 2008, and owned hedgehogs off and on for 23+ years. We maintain a small herd to focus on quality and personality. We track pedigrees on all of our hedgehogs.
You Might like
Hedgehog Care: Everything you need to know
How to prepare a hedgehog cage
I'm on the waiting list, what next?