COIs for influential sires and dams born between 1920 to 1960 (UK & US)
This page covers the inbreeding coefficients (COIs) for some of the most influential Shetland sheepdog sires and dams from the UK & US born between 1920 to 1960. These influential sires and dams are found in almost every modern pedigree, usually even several of times as Shetland Sheepdogs have a closed breed book not accepting any outside blood. It is important to study the roots of our breed and to see how much inbreeding was used in the beginning when the breed was being established during the first 10-20 generations after closing the breed books.
In a study done by Lewis et al (2015) based on the pedigree records of the UK Kennel Club, it was found that Shetland Sheepdogs have a genomic inbreeding of over 25%. This means that ”on average, the parents of a litter are as genetically similar as full siblings, even if they appear to be relatively unrelated on pedigrees” (Do you know what you need to save your breed?, Carol Beuchat PhD, 2022). Studying the influential sires and dams of our breed will give a good idea of inbreeding and the strength of selection in the early history of the breed when reviewing what happened during the first 10 generations after founding the breed. Bear in mind that these dogs have incomplete generations due to the founding stock being rather close in their pedigrees, and the founders don’t have a further pedigree recorded. I have included dogs with pedigrees going as far as 38 generations, lowest being 9 available generations.
COIs for influential sires and dams from the UK
The mean COI for influential sires and dams born in the UK between 1920 to 1960 was 19,000%. Mean COI for sires was 18,122% and for dams 19,879%. See Excel for the list of influential sires and dams included in the calculations. Most of the sires seemed to be related to each other (see Excel file for notes). Several of the dams had Chestnut Rainbow behind them, usually even several times within the five generation pedigree. Dams also had often influential sires as their sires, grandsires and great-grandsires, and some of the influential dams were also related to each other (see Excel file for notes).
The highest COI for an individual sire was 41,1369% for 13 generations (Gb Ch Blaeberry of Clerwood, 1925), and the lowest was 0,109863% for 13 generations (Gb Ch Gawaine Of Cameliard, 1926). The highest COI for an individual dam was 35,5707% for 16 generations (Gb Ch Blue Blossom of Houghton Hill, 1929), and the lowest was 0,050354% for 13 generations (Tango of Houghton Hill, 1926).
COIs for influential sires and dams from the US
The mean COI for influential sires and dams born in the US between 1920 to 1960 was 26,945%. Mean COI for sires was 34,419% and for dams 19,470%. See Excel for the list of influential sires and dams included in the calculations. Sires were generally a lot more inbred than dams, often being related to each other through other influential sires (see Excel file for notes). Dams were often related to the influential sires, and were most often a daughter or a granddaughter of an influential sire (see Excel file for notes).
The highest COI for an individual sire was 52,4233% for 19 generations (China Clipper O’ Page’s Hill ROM, 1936), and the lowest was 10,0025% for 18 generations (Am Ch Peabody Pan, 1933). The highest COI for an individual dam was 34,314% for 23 generations (Am Ch Songstress O’ Page’s Hill ROM, 1946), and the lowest was 10,2627% for 19 generations (Keep Goin’ ROM, 1933).
Resources
Carol Beuchat PhD 2022. The Institute of Canine Biology. Do you know what you need to save your breed? <https://www.instituteofcaninebiology.org/blog/do-you-know-what-you-need-to-save-your-breed>.
Carol Beuchat 2014. The Institute of Canine Biology. ICB COI Bootcamp (free course). More COI: inbred ancestors & related parents.
Gerald & Mary Fallas 1986. Shetland Sheepdog Show Champions 1915-1980.
Jan Moody 1990. Shetland Sheepdogs – The Sheltie. ISBN 0-9516812-0-6.
Pedigree Lines. US Database for Shetland Sheepdog pedigrees. <https://www.pedigreelines.com/>.
Private pedigree database of Shetland Sheepdogs. Pedigree Explorer was used for COI calculations and generating pedigrees.
Sue Ann Bowling. Shetland Sheepdog ROM Inbreeding coefficients. <https://bowlingsite.mcf.com/ROM/Inbreeding.html>.
The Breed Archive / Shetland Sheepdog. <https://sheltie.breedarchive.com/>.