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Heredity2023; 131(1); 79-85; doi: 10.1038/s41437-023-00623-8

Genetic improvement of speed across distance categories in thoroughbred racehorses in Great Britain.

Abstract: Several studies over recent decades have reported a lack of contemporary improvement in thoroughbred racehorse speed, despite apparent additive genetic variance and putatively strong selection. More recently, it has been shown that some phenotypic improvement is ongoing, but rates are low in general and particularly so over longer distances. Here we used pedigree-based analysis of 692,534 records from 76,960 animals to determine whether these phenotypic trends are underpinned by genetic selection responses, and to evaluate the potential for more rapid improvement. We show that thoroughbred speed in Great Britain is only weakly heritable across sprint (h = 0.124), middle-distance (h = 0.122) and long-distance races (h = 0.074), but that mean predicted breeding values are nonetheless increasing across cohorts born between 1995 and 2012 (and racing from 1997 to 2014). For all three race distance categories, estimated rates of genetic improvement are statistically significant and also greater than can be explained by drift. Taken together our results show genetic improvement for thoroughbred speed is ongoing but slow, likely due to a combination of long generation times and low heritabilities. Additionally, estimates of realised selection intensities raises the possibility that the contemporary selection emerging from the collective actions of horse breeders is weaker than previously assumed, particularly over long distances. We suggest that unmodelled common environment effects may have upwardly biased estimates of heritability, and thus expected selection response, previously.
© 2023. The Author(s).
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Publication Date: 2023-05-27 PubMed ID: 37244934PubMed Central: PMC10313675DOI: 10.1038/s41437-023-00623-8Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

This research paper explores the genetic improvement of speed in thoroughbred racehorses in Great Britain, concluding that despite low rates, there is still ongoing genetic progress towards faster speeds. The authors use pedigree data to evaluate potential for more rapid progress and discuss the role of several factors influencing the rate of genetic enhancement.

Research Methodology

  • The researchers utilized a pedigree-based analysis of data from 76,960 animals, retrieved from 692,534 records. The purpose was to observe any genetic selection responses linked to the phenotypic trends in thoroughbred racehorse speed.
  • The study covered racehorse cohorts born between the years 1995 and 2012, which participated in races from 1997 to 2014.
  • The analysis took into account three different race distance categories: sprint, middle-distance, and long-distance races.

Findings

  • The heritability estimates for speed in thoroughbreds across the three race distance categories were found to be weak. The heritability was estimated to be 0.124 for sprint races, 0.122 for middle-distance races, and 0.074 for long-distance races.
  • Despite the low heritability, mean predicted breeding values across the cohorts were found to be increasing, suggesting some levels of genetic progress.
  • For all three race distance categories, the researchers found that the rates of genetic improvement were statistically significant and not solely attributable to random genetic drift. However, the progress is slow.

Conclusions and Observations

  • Continued but slow genetic improvement in thoroughbred speed is potential due to a combination of long generation times and low heritabilities.
  • The study’s findings indicate that selection intensity driven by breeders may be weaker than previously anticipated, particularly in the context of long-distance races.
  • The researchers suggest that common environmental factors that were not included in the modelling might have led to overestimation of heritability and expected selection response in previous studies.

Cite This Article

APA
Sharman P, Wilson AJ. (2023). Genetic improvement of speed across distance categories in thoroughbred racehorses in Great Britain. Heredity (Edinb), 131(1), 79-85. https://doi.org/10.1038/s41437-023-00623-8

Publication

Heredity
ISSN: 1365-2540
NlmUniqueID: 0373007
Country: England
Language: English
Volume: 131
Issue: 1
Pages: 79-85

Researcher Affiliations

Sharman, Patrick
  • Centre for Ecology and Conservation, University of Exeter (Penryn Campus), Cornwall, TR10 9FE, UK. p.sharman@exeter.ac.uk.
Wilson, Alastair J
  • Centre for Ecology and Conservation, University of Exeter (Penryn Campus), Cornwall, TR10 9FE, UK.

MeSH Terms

  • Animals
  • Horses / genetics
  • United Kingdom
  • Breeding

Conflict of Interest Statement

The authors declare no competing interests.

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Citations

This article has been cited 5 times.
  1. Walz KR, McCormick ME, Fedorka CE. The Thoroughbred Theory: Influence of Breed on Performance at the CCI5*-L Level of Eventing. Animals (Basel) 2025 Jun 18;15(12).
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