Genetics coefficients: IC, AVK , RC, MK evaluations should be important and valuable to a responsible breeder
The Wright’s Inbreeding Coefficient (IC) and the Ancestor Loss Coefficient (AVK) the values are optimally IC=0 and AVK=100. A general first rule is: IC should be under 3% in a considered mating; AVK should be over 85%. A little over half of all hereditary defects are caused by hidden (recessive) genes. For the continued health of a breed it is therefore terribly important to consider in each breeding the degree of relationship represented by Relationship Coefficient (RC) in the parent dogs in order to avoid doubling up on possible defects in the alleles. The Mean Kinship Coefficient (MK) is a supplementary and it indicates in defined population the individual with the lowest MK. Individual with the lowest MK coefficient is the most genetically valuable for breeding program.
WRIGHT’s INBREEDING COEFFICIENT (IC)
Inbreeding coefficient IC (other abbreviation used in literature: WIC, IK, COI, FX, F ) can theoretically range from 0 to 100%, and shows the degree of relationship between the perspective parent dogs and indicates the possibility that two alleles of a gene are completely alike with another dog in the pedigree, i.e. they originate from the doubling of an allele in one of the ancestors. The primary consequence of inbreeding is to increase homozygosity. The inbreeding coefficient is a function of the number and location of the common ancestors in a pedigree. According to the experts is also recommended that an individual’s IC should not exceed 6% counted from the 5 generation pedigree, which is about the same as breeding among cousins, and 9% counted from the 10 generations pedigree.
FCI recommendation for rare breeds is that IC should not exceed 10%.
Wright’s equation for calculating the Inbreeding Coefficient as devised by Sewell Wright in 1922 is:
Fx is the inbreeding coefficient of the dog in question, Fa is the inbreeding coefficient of the common ancestor, n1 is the number of generations from the sire to the common ancestor, and n2 is the number of generations from the dam to the common ancestor. Since the inbreeding-coefficient (IC) shows only the relation between 2 dogs, out of a match of 2 highly inbred dogs (e.g. a match of 2 littermates) which themselves come out of 2 non-related parent-dog-bloodlines, we can get an IC nearly 0% (because there are no common ancestors in the sire's/dam's bloodline). A very simple method to overcome this problem is the calculation of the AVK. This method doesn't replace the calculation of the IC but gives for the enough information for the average breeder.
ANCESTOR LOSS COEFFICIENT (AVK) Indicates to us the suspected loss of ancestors, when computed with which one can reconstruct the in-breeding in earlier generations. The AVK for n-generation family tree is calculated by the number of actual (independent - unrepeatable) ancestors, and the total number of possible ancestors. Responsible breeder values the health of their animals (and future puppies) and are ready to pursue this information as the demand for this marvelous breed increases and further need for continued good health of the breed increases with that demand.
RELATIONSHIP COEFFICIENT (RC)
A measure of pedigree relationship. The probable proportion of one individual's genes, that are identical by descent to genes of a second individual. The correlation between the breeding values of two individuals due to pedigree relationship alone. The coefficient of relationship (RC) provides a way of objectively assessing the similarity of two pedigrees by giving a number that is a direct measure of shared ancestry. In most populations, two individuals picked at random would likely have a RC of 0, a brother and sister 50% and identical twins 100%. Other relationships would fall between 0 and 50%.
The formula for the RC is:
where ICAB is the inbreeding coefficient of a hypothetical litter between A and B, and ICA and ICB are the inbreeding coefficients for the two individuals, A and B.
MEAN KINSHIP COEFFICIENT (MK)A mean kinship (MK) value is calculated for each dog in the population using a formula. Mean kinship gives a numerical value to how closely related each dog is to the population. This gives us an important measure of just how rare an individual dog's unique combination of genes is in the entire population. Dogs with a lower mean kinship values have relatively fewer genes in common with the rest of the population, and are therefore more genetically valuable in a breeding program.The formula for the MKi for individual i is
the average of the inbreeding coefficients (fij) between i and all the other breedable individuals (It doesn't matter if they are the same sex.) in the population.
WRIGHT’S INBREEDING COEFFICIENT OF THE POPULATION
According to the experts, the IC of the population shouldn’t rise over 0.5% on a yearly basis or over 2.5% in five years time.
Summarized and prepared by: Wieslawa Jezewska
1. John B. Armstrong, 1998, 1999 Significant Relationships (http://www.canine-genetics.com/relation.htm)
2. Hundezüchtung in Theorie und Praxis von Walter Schleger und Irene Stur; ISBN 3-224-1 7000-8 Jugend und Volk Wien