Evaluation of genetic diversity using 31 microsatellites in Miyako horses.
Abstract: The Miyako horse is a native Japanese horse breed. As with other native Japanese horses, the number of Miyako horses decreased due to mechanization and motorization, which reduced their roles, with just 14 in 1980. Although their population had increased to 55 horses by 2021, a further increase in their numbers is required to avoid extinction. Recently, their breeding has involved natural mating during group grazing; therefore, pedigree management has been difficult, and individual identification has been inconclusive. With the aim of formulating an effective breeding plan, this study used microsatellites to confirm parent-offspring relationships and evaluate the genetic diversity over time. First, the combination of microsatellite genotypes identified misunderstood parent-offspring relationships in 35.3% of the existing individuals, and a correct family tree was reconstructed. Next, the number of alleles and observed and expected values of heterozygosity were calculated separately for the populations during periods of 1998-2012 and 2013-2020. The values were 4.2, 0.705, and 0.653 and 3.9, 0.633, and 0.603, respectively, indicating that genetic diversity according to all indices decreased during period of 2013-2020. This was probably because of the bias of stallions in the 2013-2020 population. Errors in pedigree information in a small population such as Miyako horses could increase the risk of inbreeding, and confirmation of parent-offspring relationships using genotypes may be beneficial. Additionally, to maintain diversity in future breeding, it is important to avoid bias, particularly among stallions, and to ensure offspring of various individuals who are as distantly related to each other as possible.
©2023 The Japanese Society of Equine Science.
Publication Date: 2023-03-24 PubMed ID: 37155490PubMed Central: PMC10122988DOI: 10.1294/jes.34.1Google Scholar: Lookup
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Summary
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The study is about assessing the genetic diversity of the Miyako horse, a native Japanese breed, to mitigate their risk of extinction and to develop an effective breeding plan. The researchers used microsatellites for confirming parent-offspring relationships and to evaluate genetic diversity over time.
About the Miyako Horse
- The Miyako horse is a Japanese native breed whose population dwindled due to factors such as motorization and mechanization. By 1980, only 14 Miyako horses were left.
- The numbers have increased since then, reaching 55 horses in 2021, but further increase is critical for their continued survival.
- The horses have been breeding naturally during group grazing, resulting in challenging pedigree management and inconclusive individual identification.
Methodology: Using Microsatellites
- The research made use of microsatellites (areas of repeating DNA in a genome) to verify parent-offspring relations and assess genetic diversity over time.
- Microsatellites were effective in identifying previously misunderstood parent-offspring relationships in 35.3% of individuals, leading to a successful re-establishment of the correct family tree.
Results and Findings
- The study drew information from two periods, 1998-2012 and 2013-2020, calculating the number of alleles and the observed and expected heterozygosity values.
- The genetic diversity, according to all indices, saw a decline over the period of 2013-2020 compared to the period of 1998-2012. This is likely due to a bias in the stallions’ contributions to the population during the more current period.
Implications and Future Recommendations
- Errors in pedigree data in a small population, such as the Miyako horses, can inadvertently increase the risk of inbreeding. Hence, confirmation of parent-offspring relationships using genetic markers is beneficial.
- To preserve genetic diversity for future breeding, it’s crucial to prevent bias particularly amidst stallions and ensure offspring from a wide array of individuals who share as little relation as possible.
Cite This Article
APA
Masuda M, Nikadori A, Nikadori E, Uchida N, Takizawa Y, Ishimaru M, Yamamoto T, Yuasa R, Kugai H, Nagahama Y, Takasu M, Tozaki T.
(2023).
Evaluation of genetic diversity using 31 microsatellites in Miyako horses.
J Equine Sci, 34(1), 1-6.
https://doi.org/10.1294/jes.34.1 Publication
Researcher Affiliations
- Nikadori Ranch, Okinawa 906-0013, Japan.
- Nikadori Ranch, Okinawa 906-0013, Japan.
- Nikadori Ranch, Okinawa 906-0013, Japan.
- VET Co., Ltd. Miyako Veterinary Clinic, Okinawa 906-0106, Japan.
- Japan Racing Association, Tokyo 105-0003, Japan.
- Japan Racing Association, Tokyo 105-0003, Japan.
- Japan Racing Association, Tokyo 105-0003, Japan.
- Japan Racing Association, Tokyo 105-0003, Japan.
- Miyako Horse Conservation Society, Okinawa 906-8501, Japan.
- Miyakojima City History Compilation Committee, Okinawa 906-0011, Japan.
- Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University, Gifu 501-1193, Japan.
- Department of Veterinary Medicine, Faculty of Applied Biological Sciences, Gifu University, Gifu 501-1193, Japan.
- Genetic Analysis Department, Laboratory of Racing Chemistry, Tochigi 320-0851, Japan.
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