Masuda Mioko, Nikadori Akihiro, Nikadori Emi, Uchida Naoya, Takizawa Yoshimasa, Ishimaru Mutsuki, Yamamoto Takumi, Yuasa Reiko, Kugai Haruo, Nagahama Yukio, Takasu Masaki, Tozaki Teruaki
Nikadori Ranch, Okinawa 906-0013, Japan.
VET Co., Ltd. Miyako Veterinary Clinic, Okinawa 906-0106, Japan.
J Equine Sci. 2023 Mar;34(1):1-6. doi: 10.1294/jes.34.1. Epub 2023 Mar 24.
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.
宫古马是日本本土的马种。与其他日本本土马一样，由于机械化和机动化减少了宫古马的作用，其数量有所下降，1980年时仅剩下14匹。尽管到2021年其数量已增至55匹，但仍需要进一步增加数量以避免灭绝。最近，它们的繁殖采用了群体放牧时自然交配的方式；因此，谱系管理变得困难，个体识别也尚无定论。为了制定有效的繁殖计划，本研究使用微卫星来确认亲子关系，并评估随时间变化的遗传多样性。首先，微卫星基因型的组合在35.3%的现有个体中识别出了被误解的亲子关系，并重建了正确的家族树。接下来，分别计算了1998 - 2012年和2013 - 2020年期间种群的等位基因数量、杂合度的观察值和预期值。这些值分别为4.2、0.705和0.653以及3.9、0.633和0.603，表明在2013 - 2020年期间，所有指标的遗传多样性都有所下降。这可能是由于2013 - 2020年种群中种马的偏差。像宫古马这样的小种群中谱系信息的错误可能会增加近亲繁殖的风险，使用基因型确认亲子关系可能会有所帮助。此外，为了在未来的繁殖中保持多样性，避免偏差，特别是种马之间的偏差，并确保尽可能远亲的不同个体的后代非常重要。
