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Inbreeding in the Thoroughbred horse.
Abstract: Changes in the inbreeding coefficient, F, in the Thoroughbred horse over the past 45 years have been investigated by genotyping 467 Thoroughbred horses (born between 1961 and 2006) using the Illumina Equine SNP50 bead chip, which comprises 54,602 SNPs uniformly distributed across the equine genome. The Spearman rank correlation coefficient, r, between the year of birth and F was estimated. The results indicate that inbreeding in Thoroughbreds has increased over the past 40 years, with r = 0.24, P < 0.001 demonstrating that there is a highly significant, though relatively weak correlation between the year of birth and inbreeding coefficients. Interestingly, the majority of the increase in inbreeding is post-1996 and coincides with the introduction of stallions covering larger numbers of mares.
© 2011 The Authors, Animal Genetics © 2011 Stichting International Foundation for Animal Genetics.
Publication Date: 2011-11-08 PubMed ID: 22486509DOI: 10.1111/j.1365-2052.2011.02259.xGoogle Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
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The research explores the change in inbreeding levels, identified by the coefficient F, in Thoroughbred horses over 45 years. The study indicates inbreeding has increased, correlating most significantly after 1996, which aligns with the practice of male horses breeding with larger numbers of mares.
Study Sample and Methodology
- The researchers focused their study on the Thoroughbred horse, a popular breed globally, especially in racing activities.
- The genetic data of 467 Thoroughbred horses, born between 1961 and 2006, were genotyped with the help of Illumina Equine SNP50 bead chip. This bead chip includes 54,602 Single Nucleotide Polymorphisms (SNPs), which are effectively dispersed across the horse’s genome.
- The study spanned over a period of 45 years, providing a comprehensive overview of possible changes in inbreeding levels in the breed.
Findings and Interpretations
- After analyzing the collected data, the results revealed a steady increase in the inbreeding coefficient, denoted as F, over the past 40 years within the Thoroughbred horse population.
- The statistical analysis showed a Spearman rank correlation coefficient, r, of 0.24, with P < 0.001. This result is highly statistically significant, suggesting a credible correlation exists between the year of birth of Thoroughbred horses and their inbreeding coefficients.
- While this correlation is not very strong, it is statistically worthwhile, pointing to a growth in inbreeding levels over the examined years.
Post-1996 Observations
- The research also discovered that the primary surge in inbreeding occurred post-1996, a period that coincides with the increased use of select stallions to cover, or mate with, larger numbers of mares.
- This finding suggests the widespread practice of using a single stallion for breeding with multiple mares may have unintentionally accelerated the level of inbreeding within the Thoroughbred population.
Implications for the Future
- The study’s results serve to underline the importance of genetic diversity in horse breeding, highlighting potential genetic risks associated with widespread inbreeding.
- The research may prompt breeders to adjust their practices to curb this increasing trend of inbreeding in Thoroughbreds, which could possibly lead to detrimental health effects in the breed over time due to reduced genetic diversity.
Cite This Article
APA
Binns MM, Boehler DA, Bailey E, Lear TL, Cardwell JM, Lambert DH.
(2011).
Inbreeding in the Thoroughbred horse.
Anim Genet, 43(3), 340-342.
https://doi.org/10.1111/j.1365-2052.2011.02259.x Publication
Researcher Affiliations
- Equine Analysis, Midway, KY 40347, USA. mbinns@equineanalysis.com
MeSH Terms
- Animals
- Female
- Genotype
- High-Throughput Nucleotide Sequencing
- Horses / genetics
- Inbreeding
- Male
- Pedigree
- Statistics, Nonparametric
- Time Factors
Citations
This article has been cited 10 times.- Próchniak T, Kasperek K, Knaga S, Rozempolska-Rucińska I, Batkowska J, Drabik K, Ziȩba G. Pedigree Analysis of Warmblood Horses Participating in Competitions for Young Horses. Front Genet 2021;12:658403.
- Kalashnikov V, Khrabrova L, Blohina N, Zaitcev A, Kalashnikova T. Dynamics of the Inbreeding Coefficient and Homozygosity in Thoroughbred Horses in Russia. Animals (Basel) 2020 Jul 17;10(7).
- McGivney BA, Han H, Corduff LR, Katz LM, Tozaki T, MacHugh DE, Hill EW. Genomic inbreeding trends, influential sire lines and selection in the global Thoroughbred horse population. Sci Rep 2020 Jan 16;10(1):466.
- McHugo GP, Browett S, Randhawa IAS, Howard DJ, Mullen MP, Richardson IW, Park SDE, Magee DA, Scraggs E, Dover MJ, Correia CN, Hanrahan JP, MacHugh DE. A Population Genomics Analysis of the Native Irish Galway Sheep Breed. Front Genet 2019;10:927.
- Grilz-Seger G, Neuditschko M, Ricard A, Velie B, Lindgren G, Mesarič M, Cotman M, Horna M, Dobretsberger M, Brem G, Druml T. Genome-Wide Homozygosity Patterns and Evidence for Selection in a Set of European and Near Eastern Horse Breeds. Genes (Basel) 2019 Jun 28;10(7).
- Kim NY, Seong HS, Kim DC, Park NG, Yang BC, Son JK, Shin SM, Woo JH, Shin MC, Yoo JH, Choi JW. Genome-wide analyses of the Jeju, Thoroughbred, and Jeju crossbred horse populations using the high density SNP array. Genes Genomics 2018 Nov;40(11):1249-1258.
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- Kapusniak A, Nath L, Hebart M, Franklin S. Heritability of sudden cardiac death in Thoroughbred racehorses. Equine Vet J 2025 Mar;57(2):325-332.
- Sobotková E, Kopec T, Mikule V, Kuřitková D. Influence of horse demographics, country of training and race distance on the rating of Thoroughbreds. Arch Anim Breed 2023;66(4):299-313.
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