COEFFICIENT OF INBREEDING

Reprinted from page 21 of the November 1998  issue of the SSDCA NEWSLETTER, written by Tina Barber

 

 

Since some very strange genetic health problems started surfacing recently, I was determined to research the pedigrees of the effected dogs in hopes of some answers. My kitchen table soon proved to be much too small to contain the volumes of paper I was using, trying to go back only 9 generations! Since all of the Shilohs are already heavily "linebred" and some breedings now taking place are intensifying this problem even more, I wanted to determine the coefficients, since such breedings increase the occurrence of deleterious recessive traits. I had spent several months discussing our lines with an expert geneticist, and he recommended a program that Cornell University, as well as many others, have been using. Since I was not getting very far with my kitchen table & calculator, I figured I would look into his suggestion. It has taken me awhile to get "familiar" with using only a small part of the program, but the data that I have been seeing is absolutely amazing!

We are all aware of the "dark side of inbreeding," and I even mentioned some of the problems that could arise from incomplete data on "past generations" in my other article. Mr. Fred Lanting states that "In livestock breeding, 6.25% is often used as an upper limit for an acceptable level of inbreeding in a population." He has also advocated that clubs maintain a geneticist "to keep track of the kinship or inbreeding coefficients." In order to prevent defective homozygotes (an organism that possesses identical alleles at a given gene locus) it is imperative to determine the inbreeding coefficient (a number used to qualify the PROBABILITY that an organism will have identical alleles from the same ancestral source). The program I am using even provided the Homozygous %, up to 30 generations! In a 30-generation pedigree the maximum possible ancestors is 2,147,483,646. !! So far we have close to 45,000 of these programmed in, with more to be added shortly.

1/99 Update; I have completed my preliminary evaluations of the popularly used Shiloh Shepherd genepool. When randomly selecting reports from a pile of over 100, the following Relationship Coefficient % had been calculated as 49.267, 36.269, 52.026, 34.598, 28.167, 63.526, 45.248. Upon closer examination I discovered that most ranged in the mid-high 30's. Only 4 were found that averaged in the low 20's, and over 1/3rd ran well over 40%. The lowest RC found was 14.729 (from a NB breeding) the highest found was 68.329.




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