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ばんえい競走馬獲得賞金の遺伝率

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Adjustments for variability and their impact on heritability estimates of

the earnings of Banei racing horses

Airi KURAKAMI1, Yuka NAKAHORI1, Naoki TAKANO2, Fumiaki OHE3 and Koichi HAGIYA1

Obihiro University of Agriculture and Veterinary Medicine, Obihiro 080-8555, Japan

Hokkaido University, Sapporo 060-0808, Japan

Hokkaido Yusen Hoso KK, Obihiro 080-0023, Japan

Corresponding : Koichi HAGIYA (e-mail : hagiya@obihiro.ac.jp)

Here, we examined the impact of adjustments of variability on heritability estimates of the earnings

of 2-year-old Banei racing horces. Data of 2302 Banei racing horses born in the period 2005–2014, and

the pedigree records of 27,215 animals were used in our statistical analyses. The records of Banei

racing horses contained sex, year and month of birth, date of performance testing, and earnings at 2

year of age. The variability of earnings at 2 years of age was adjusted by log-transformation or

stratification into 3, 5 or 7 classes. An animal model that included sex, birth year, and age at the time of

performance testing as fixed effects, and additive genetic effects and residuals as random effects, was

used to estimate genetic parameters. Age at the time of performance testing was estimated by using

the date of the performance testing and the birth month. The heritability estimates of log-transformed

earnings (0.29) was higher than that of untransformed earnings (0.16). The heritability estimates when

earnings were stratified into 3, 5, or 7 classes were in the range 0.32–0.36. Thus, the present results

suggest that higher heritability estimates are obtained when the variability of earnings is adjusted.

Nihon Chikusan Gakkaiho 91 (3), 179-183, 2020

Key words : Banei racing horse, earnings, heritability.

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