Inbreeding Coefficients

Calculations presented here are meant to assist fanciers who wish to limit (or increase) the degree of inbreeding in their programs. No attempt is made to discuss or imply the virtues of inbreeding. However, while inbreeding may increase homozygosity (double up) of favorable genes, it may also produce a loss of vigor and an increase in the probability of unfavorable recessive health related issues. Fanciers are left on their own to determine just how much inbreeding they wish to pursue. For those of you who wish to read more on this topic you can find extensive explanations of inbreeding coefficients on the Internet. Simply make an Internet search on Wright's Coefficients of Inbreeding, etc.

Calculations of three commonly used inbreeding coefficients are made for the fancier's use. The inbreeding coefficients calculated are Wright's Coefficient of Inbreeding (COI), Wright's Coefficient of Relationship (COR) and Ancestor Loss Coefficient (AVK). Inbreeding coefficients are a function of the number and location of the common ancestors in a pedigree. It is important that the fancier enter as much of the pedigree as known in order to calculate more accurate results.

COI is probably the most commonly used of the inbreeding coefficients. It was developed by Sewell Wright in 1921. In order for a bird (or proposed pairing) to receive a COI score higher than "0" the pedigree must contain a common ancestor in the sire's and dam's pedigree. If there are multiple common ancestors the values for each is calculated and then added. The resulting calculations are presented as a percentage. The higher the percentage the more intense the inbreeding.

The "COI" button located on the Pedigree and Pairing pages will calculate the three inbreeding coefficients. Clicking on the COI button will display the results for each coefficient. The OK button then returns you to the pedigree or pairing page depending upon where you started. After clicking the COI button you chose the Stats button instead of OK you will find the various common ancestors used for the COI calculation and the percent assigned to each. Also presented is the pedigree path for each common ancestor used in the calculation using the circuit method developed by Paul Rogers, 2003. There is a summary at the bottom of the Stats page.

COI example results assuming no commonality other than that stated:

  • Total out cross: 0%
  • Half brother/sister where there are nor more common ancestors: 12.5%
  • Full brother/sister: 25%:
  • Father to daughter or mother to son: 25%
  • Aunt to nephew or uncle to niece: 12.5%
  • Half aunt to nephew or half uncle to niece: 6.25%
  • Full first cousins: 6.25%
  • Half first cousins: 3.125%

LoftManager Online and COI

COI calculations are performed to 10 generations for a particular mating. To learn more about COI, use a search engine such as Google, and search for "Wright's Coefficient of Inbreeding". (Google COI)

On the Pedigree tab, COI can be calculated using the COI button. On the Pairing tab, COI is shown automatically when both the sire and dam have been chosen. The COI button on the Pairing tab will show you the details.

The COI dialog box:
COI Dialog Box


The COI Details dialog box:
COI Details Dialog Box

In the 'details' we also show you the raw Ancestor Loss Coefficient (AVK) (Google AVK) for a particular bird or mating and the Coeffiecient of Relationship (COR) of the birds in that mating.