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Home / Equine Research Bank / J Equine Sci / Demographic analysis of breeding structure in Japanese thoro...
Journal of equine science2010; 21(2); 11-16; doi: 10.1294/jes.21.11

Demographic analysis of breeding structure in Japanese thoroughbred population.

Abstract: To investigate the breeding structure in the Japanese Thoroughbred population, we applied a demographic analysis to the populations of foals produced from 1978 to 2005. The migration rate estimated from the proportion of foals produced by imported breeding horses was around 40% over the investigated period. After early 1990s, the migration rate through stallions imported from USA sharply increased. The average generation interval was within range of 10.5-11.5 years. The longer generation interval of Thoroughbred was considered to be a reflection of the fact that Thoroughbred horses begin breeding only after completing their performance in races. After the peak of 729 in 1993, the number of sires of foals progressively declined to 358 in 2005. Although the coefficient of variation of the progeny number of sires was within range of 1.0-1.2 until early 1990s, it gradually increased and reached the value of 1.6-1.7 in recent years. The effective number of sires consistently decreased after the peak of 302.6 in 1992, and reached 120-130 in recent years, which is 25-30% of the actual number of sires. In parallel, the demographic estimate of the effective population size declined after early 1990s. The main cause of the observed change in the breeding structure was inferred to be the intensive use of a limited number of stallions for breeding.
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Publication Date: 2010-07-16 PubMed ID: 24833974PubMed Central: PMC4013955DOI: 10.1294/jes.21.11Google Scholar: Lookup
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Summary

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The research article is a detailed study of the breeding structure of the Japanese Thoroughbred horse population from 1978 to 2005, with a focus on factors like migration rate, generation interval, number of sires, and effective population size.

Investigation Methodology and Key Findings

  • The researchers conducted a demographic analysis on the population of foals that were born between 1978 and 2005 in the Japanese Thoroughbred population.
  • The migration rate of this population over this period, estimated from the proportion of foals born from imported breeding horses, was found to be around 40%.
  • A notable increase in the migration rate through stallions imported from the USA was observed after the early 1990s.

Thoroughbred Generation Interval

  • The average generation interval in this population was found to be between 10.5-11.5 years. This relatively long generation interval for Thoroughbreds is due to the tradition of Thoroughbred horses only starting to breed after finishing their racing careers.

Changes in Sires Numbers and Progeny Variation

  • The research notes a decline in the number of sires of foals after a peak in 1993. The number progressively decreased from 729 in 1993 to 358 in 2005.
  • Simultaneously, it was observed that even though the coefficient of variation of the progeny number of sires was between 1.0-1.2 until the early 1990s, it gradually increased, reaching a value of 1.6-1.7 in recent years.
  • The effective number of sires observed a consistent decrease after a peak in 1992, falling to between 120 and 130 in recent years, which equates to 25-30% of the actual number of sires.

Effective Population Size and Root Cause

  • The effective population size, as estimated by demographic research, also displayed a decline after the early 1990s.
  • The researchers attributed the changes observed in the breeding structure to the intensive use of a limited number of stallions for breeding purposes.

Cite This Article

APA
Yamashita J, Oki H, Hasegawa T, Honda T, Nomura T. (2010). Demographic analysis of breeding structure in Japanese thoroughbred population. J Equine Sci, 21(2), 11-16. https://doi.org/10.1294/jes.21.11

Publication

Journal of equine science
ISSN: 1340-3516
NlmUniqueID: 9503751
Country: Japan
Language: English
Volume: 21
Issue: 2
Pages: 11-16

Researcher Affiliations

Yamashita, Jun
  • Department of Biotechnology, Faculty of Engineering, Kyoto Sangyo University, Kita-ku, Kyoto 603-8555, Japan.
Oki, Hironori
  • Equine Research Institute, Japan Racing Association, 321-4 Tokami-cho, Utsunomiya, Tochigi 320-0856, Japan.
Hasegawa, Telhisa
  • Equine Research Institute, Japan Racing Association, 321-4 Tokami-cho, Utsunomiya, Tochigi 320-0856, Japan.
Honda, Takeshi
  • Food Resources Education and Research Center, Graduate School of Agricultural Science, Kobe University, 1348 Uzurano-cho, Kasai, Hyogo 675-2103, Japan.
Nomura, Tetsuro
  • Department of Bioresource and Environmental Sciences, Faculty of Life Sciences, Kyoto Sangyo University, Kita-ku, Kyoto 603-8555, Japan.

References

This article includes 12 references
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Citations

This article has been cited 1 times.
  1. Yamashita J, Oki H, Hasegawa T, Honda T, Nomura T. Gene dropping analysis of ancestral contributions and allele survival in Japanese thoroughbred population. J Equine Sci 2010;21(3):39-45.
    doi: 10.1294/jes.21.39pubmed: 24833977google scholar: lookup
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