Pedigree analysis of four decades of Quarter Horse breeding.
Abstract: Pedigrees of randomly selected Quarter Horses born in each of the years 1946, 1956, 1966 and 1976 and of winning halter, cutting and race horses born in the same years were evaluated and compared. Average inbreeding and inter se relationship levels and relationships of influential ancestors to the sample were calculated for each sample. The amount of Thoroughbred influence and the average generation interval were also determined for each random sample. The levels of inbreeding found in the random samples were low, ranging from 1.3% in 1956 to 2.6% in 1966; however, these levels were higher than would be expected if mating were random. Show and race winners born in 1976 appeared to be less inbred than random horses of the breed. The estimated average inter se relationship within the random samples increased from 0% in 1946 to 3% in 1966, decreasing again to 0% in 1976. Horses in the elite samples appeared to be more closely related to each other than those in the random samples. Fifteen ancestors of horses in the random samples were identified as influential to the Quarter Horse breed. Many of these same ancestors were influential in the halter and cutting samples, but only one was influential in the race samples. The percentage of pedigree lines in the random samples that contained a Thoroughbred ancestor were as follows; 1946, 27.5%; 1956, 19.2%; 1966, 23.2% and 1976, 31.4%. The average generation interval fluctuated from approximately 8 yr to approximately 10 yr for the random samples.
Publication Date: 1983-09-01 PubMed ID: 6630095DOI: 10.2527/jas1983.573585xGoogle Scholar: Lookup
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- Journal Article
Summary
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This research article analyzes the genetic makeup and influence of Quarter Horses over four decades, considering a variety of factors such as inbreeding levels, relationships between ancestors and Thoroughbred influences.
Objective of the Study
- The objective of the study was to evaluate and compare the pedigrees of randomly selected Quarter Horses born in the years 1946, 1956, 1966, and 1976.
- The study also looked at Quarter horses who were successful at halter (a discipline requiring a horse to be led by a handler), cutting (where a horse separates a single animal from a herd), and racing competitions in the same years.
Research Findings and Analysis
- The research found low levels of inbreeding in the samples, ranging from 1.3% to 2.6% across the years. These percentages, however, were higher than would be expected if the mating were randomly done, indicating some level of controlled breeding techniques were used.
- The competition-winning horses born in 1976 seemed to be less inbred compared to the non-winning horses of the same breed and birth year.
- The average inter se relationship, or how closely the horses were related to each other, within the random samples increased from 0% in 1946 to 3% in 1966, and then decreased again to 0% in 1976. This drop in relationship levels shows that breeders were introducing a greater genetic diversity into their breeding programs by 1976.
- Elite horses, or those that fared well in competition, appeared to be more closely related to each other than those in the random samples, suggesting a genetic basis for their success.
Influence of Ancestors and Thoroughbred Contribution
- Fifteen ancestors in the random samples were discovered to be influential to the Quarter Horse breed, having left a significant genetic legacy. Many of these ancestors were also influential in the halter and cutting samples, but only one was influential in the racing samples.
- The study also found a substantial contribution from Thoroughbred horses to the Quarter Horse breed, fluctuating from 19.2% to 31.4% across all the years in the random samples.
Generation Interval
- The average generation interval, or the average age at which an animal is replaced by its offspring in the breeding population, varied from approximately 8 years to 10 years for Quarter Horses in the random samples.
Cite This Article
APA
Tunnell JA, Sanders JO, Williams JD, Potter GD.
(1983).
Pedigree analysis of four decades of Quarter Horse breeding.
J Anim Sci, 57(3), 585-593.
https://doi.org/10.2527/jas1983.573585x Publication
Researcher Affiliations
MeSH Terms
- Animals
- Breeding
- Female
- Horses / genetics
- Inbreeding
- Male
- Pedigree
- United States
Citations
This article has been cited 2 times.- Bartolomé E, Valera M, Fernández J, Rodríguez-Ramilo ST. Effects of Selection on Breed Contribution in the Caballo de Deporte Español.. Animals (Basel) 2022 Jun 25;12(13).
- Petersen JL, Mickelson JR, Cleary KD, McCue ME. The American Quarter Horse: population structure and relationship to the thoroughbred.. J Hered 2014 Mar-Apr;105(2):148-62.
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