著者

Toshiyuki TAKAHASHI Osamu AOKI Atsushi HIRAGA

出版者

Japanese Society of Equine Science

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.18, no.2, pp.47-53, 2007 (Released:2007-07-11)

参考文献数

9

被引用文献数

1 2

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The purpose of this study was to describe the characteristics of fast race horses by analyzing the running form of Deep Impact, the undefeated Japanese triple crown winner in 2005. A high-speed video data of the Kikuka Syo race (Japanese St. Leger, JPN G1, 3,000 m, turf) was taken at a rate of 250 frames/sec. The high-speed video system was set in a left lateral position about 100 m before the finishing post with a field view width of about 16 m. The speed of Deep Impact, 17.8 m/sec, was the fastest of all horses measured (average 16.1 m/sec), the stride frequency, 2.36 strides/sec, was the third largest (average 2.28 strides/sec), and the stride length, 7.54 m, was the longest (average 7.08 m). The diagonal and airborne step lengths of Deep Impact were longer than the average values. The overlap time of Deep Impact was shorter than the average value. The ratio of overlap time to stride duration of Deep Impact was 8.5 %, whereas the average value was 16.9 %. A shorter overlap time was also observed on a common characteristic of Secretariat, the famous elite race horse in USA and correlated to running speed. Thus, these characteristics may be related to effective running form in elite horses.

著者

Kazuhiro KAMIYA Hajime OHMURA Daisuke ETO Kazutaka MUKAI Shigeto USHIYA Atsushi HIRAGA Sadao YOKOTA

出版者

Japanese Society of Equine Science

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.14, no.3, pp.97-100, 2003 (Released:2003-12-19)

参考文献数

13

被引用文献数

1

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T. M. Opera O is considered as one of the greatest racehorses in the history of horseracing in Japan. Only a very few data is available on circulatory function of elite Thoroughbred racehorses. Recently, we obtained data on circulatory parameters of T. M. Opera O. The left ventricular mass of T. M. Opera O, as measured on an echocardiogram, was 4.60 kg. The resting heart rate (HR) of T. M. Opera O was 25 beat/min. The low-frequency and high-frequency power, as determined by an analysis of HR variability, were 13,900 and 5.963 ms2, respectively, which were considerably higher than those of the other racehorses. These results suggest that a large heart, formed by genetic factors and training, markedly enhanced the parasympathetic nervous activity and reduced the resting HR of T. M. Opera O. The data we obtained from T. M. Opera O is invaluable for understanding the physical fitness of elite Thoroughbreds and for further developing their athletic performance.

著者

Ayumi TEZUKA Masaki TAKASU Teruaki TOZAKI Atsushi J. NAGANO

出版者

Japanese Society of Equine Science

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.30, no.2, pp.33-40, 2019 (Released:2019-07-03)

参考文献数

10

被引用文献数

1 2

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Taishu horses are a native Japanese breed, of which only 41 individuals remained on Tsushima Island in 2018. Their genetic diversity is considered lower than that of other Japanese native horse breeds; thus, it needs to be investigated for sustainable conservation of this breed. Historical records revealed that several Taishu individuals were released areas off-Tsushima Island in mid-1980s. At present, Taishu horses living outside of Tsushima Island, hereafter referred to as Non-Tsushima Taishus (NTTs), are tagged. However, the genetic structure of the NTT individuals remains unclear, and such individuals are not included in the current mating plans for Taishu horses. Herein, we examined the genetic structure of 18 NTT individuals by comparing their genomic (SNP) information with that of individuals on Tsushima Island (TT), four other native Japanese breeds, and one Anglo-Arabian breed by using ddRAD-seq. We found that all individuals related to the Taishu can be grouped in one cluster, which was separated from other horse breeds. Patterns of specific and shared SNPs in NTT individuals closely resembled those of TT individuals, suggesting very minor genetic differences. Meanwhile, the heterozygosity of NTT individuals was slightly higher than that of TT individuals, and many NTT individuals were of fertile age, suggesting that the pedigree of NTT individuals would be useful in breed conservation plans for Taishu horses. Based on their genomic information, we also reconstructed the pedigree structures of four NTT individuals with no family information. The inclusion of NTT individuals in future mating plans on Tsushima Island may be an effective and feasible method for conserving the Taishu horse breed in Japan.

著者

Fumiro KASHIWAMURA Avarzed AVGAANDORJ Keiko FURUMURA

出版者

日本ウマ科学会

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.12, no.1, pp.1-7, 2001 (Released:2001-10-27)

参考文献数

13

被引用文献数

3 16

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The body size and weight of 584 Banei draft racehorses at Obihiro Racing Stable in Hokkaido, Japan, was investigated. Almost all the animals (94.7%) were cross-breed heavy draft horses; there were a few Percheron and Percheron grade (4.8%) and a Belgian breed (0.5%). The ages of the animals ranged from 2 to 10 years. Males accounted for 80.3%, females for 17.5%, and 2.2% were castrated. The mean body measurements of 2-year-old Banei draft racehorses were significantly smaller than those of the 3-to 4-year-old or 5-to 10-year-old horses. Hip width, croup width, and rump length of females were greater than those of males. In contrast, males had greater chest width and cannon bone circumference than females. Significant relationships among almost all body measurements were observed. A high correlation was found between body weight and chest girth, croup width and body length. A principle component analysis were applied to investigate the effect of body conformation on racing performance in terms of earnings and the time on the performance test. Performance was significantly related to the principle components of general body size and weight of the horses. The cannon bone, body length, and rump length were suggested to have an effect on earnings per race in 2-year-old male horses. In terms of body size and conformation, the Banei draft racehorses, which are large in general size and well balanced, seemed to show high performance.

著者

平賀 敦 山野辺 啓 久保 勝義

出版者

Japanese Society of Equine Science

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.5, no.4, pp.127-130, 1995-03-31 (Released:2011-11-29)

参考文献数

5

被引用文献数

6 8

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この研究の目的は,競走馬のスタートダッシュ時のストライド幅,ストライド数,隣接した2蹄跡間の歩幅であるステップレングス(Steplength)と速度との関係を知ることであった.ストライド数は最初の数完歩に若干の変動を認めるものの,スタート直後からほぼ最大レベルで一定となったのに対し,ストライド幅は25-30完歩でほぼ最大に達した.このことから,実質的な速度増加はストライド幅の増加によるものの,スタート直後ではストライド数を最大にすることの貢献が大きいものと思われた.ステップレングスについては,Mid step lengthが最初から最大レベルに達したのに対し,Airborne step lengthは最大に達するのに時間を要した.これは,スタート直後にAirborne step lengthを急速に増加させることができないため,Mid step lengthを最大限に増加させることにより,速度の増加を行なっていることを示しているものと思われた.

著者

Jeffrey A. FAWCETT Hideki INNAN Takeru TSUCHIYA Fumio SATO

出版者

Japanese Society of Equine Science

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.32, no.2, pp.31-37, 2021 (Released:2021-06-18)

参考文献数

18

被引用文献数

1

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Many studies have reported that advancing age in broodmares has a negative impact on the reproductive performance of horses. However, although the ages at first and last mating vary among broodmares, it is unknown how this variation affects the correlation between age and reproductive performance in mares. Here, in order to examine the effects of the ages at first and last mating, we analyzed all recorded mating events for Thoroughbreds in Japan from 1997 to 2017. We found that the live foal birth rate of mares with a younger age at first mating indeed declined at an earlier age than those with an older age at first mating and that the number of years since the first mating also contributes to the decline in the birth rate. We also found that the live foal birth rate and mean earnings of the produced foals are much higher for mares with an older age at last mating compared with mares with a younger age at last mating. Our results should aid breeders in assessing the value of broodmares and designing breeding strategies.

著者

Kousuke TANAKA Atsushi HIRAGA Toshiyuki TAKAHASHI Atsutoshi KUWANO Scott Edward MORRISON

出版者

日本ウマ科学会

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.26, no.2, pp.67-71, 2015 (Released:2015-07-02)

参考文献数

12

被引用文献数

2

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We applied aluminum hinged shoes (AHSs) to the club foot-associated contracted feet of 11 Thoroughbred yearlings to examine the effects of the shoes on the shape of the hoof and third phalanx (P III). After 3 months of AHS use, the size of the affected hooves increased significantly, reaching the approximate size of the healthy contralateral hooves with respect to the maximum lateral width of the foot, the mean ratio of the bearing border width to the coronary band width, and the mean ratio of the solar surface width to the articular surface width. These results suggest that the AHSs corrected the contracted feet in these yearling horses.

著者

Atsushi IIDA Hitomi SAITO Akihito AMAO Takuya FUJITA Atsushi KATO Fumitaka UEDA

出版者

Japanese Society of Equine Science

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.31, no.1, pp.11-15, 2020 (Released:2020-03-19)

参考文献数

21

被引用文献数

1

---

A nutritional supplement containing salacinol (NSS) was administered to Thoroughbred foals daily beginning 21 days after birth, and clinical signs and intestinal microbiota were analyzed. The average number of days for which foals exhibited a fever between 21 and 110 days after birth was determined. The number of days was significantly reduced, by approximately 1/3, in the NSS group compared with the control group. Furthermore, improved weight gain was observed in the NSS group compared with the control group. By analyzing the intestinal microbiota, it was determined that the ratio of Clostridium cluster XIVa increased after 3 weeks of NSS administration. These results demonstrate that the daily administration of NSS might improve the intestinal environment of neonatal foals and be useful for health.

著者

Fumiaki MIZOBE Yuji TAKAHASHI Kanichi KUSANO

出版者

Japanese Society of Equine Science

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.31, no.4, pp.101-104, 2020 (Released:2020-12-18)

参考文献数

14

被引用文献数

2 3

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Jockey safety is of paramount importance from the standpoint of welfare and public perception. Thus, an understanding of the epidemiology and associated risk factors is necessary to implement measures to reduce the jockey falls (JFs) and jokey injuries (JIs). This descriptive epidemiological study investigated the occurrence of JFs and JIs in 715,210 and 25,183 rides in flat and jump races, respectively, from 2003 to 2017. In flat races, the incidence rates of JFs and JIs were 1.4 and 0.6 per 1,000 rides, respectively. In jump races, they were 44.4 and 18.1 per 1,000 rides, respectively. In flat races, 56.8% of JFs at corners resulted in JIs. In jump races, the major causes of JFs and JIs were lost balance and hampered by a fallen horse at an obstacle. Our findings provide a basis to design a future study analyzing risk factors for JFs.

著者

Teruaki TOZAKI Aoi OHNUMA Mio KIKUCHI Taichiro ISHIGE Hironaga KAKOI Kei-ichi HIROTA Natasha A. HAMILTON Kanichi KUSANO Shun-ichi NAGATA

出版者

Japanese Society of Equine Science

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.31, no.4, pp.75-83, 2020 (Released:2020-12-18)

参考文献数

24

被引用文献数

6

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Gene doping is prohibited in horseracing and equestrian sports. In previous studies, we developed non-targeted transgene and genome editing detection methods based on whole genome resequencing (WGR) using genomic DNA extracted from whole blood. In this study, we aimed to develop a WGR method using DNA extracts from hair roots. Hair roots are a preferred substrate because their collection is less invasive than blood collection. Hair is also easier to store for long periods of time. Although almost all genomic DNA extracted from hair root samples stored for years at room temperature was degraded, the quality of genomic DNA from samples stored for years at refrigerated temperatures (4–8°C) was maintained. High-molecular-weight genomic DNA was isolated from hair roots using a magnetic silica beads method of extraction, enabling WGR from horsehair root extracts. Nucleotide sequencing results and numbers of single-nucleotide polymorphisms and insertions/deletions concurred with those previously reported for WGR of DNA extracted from whole blood. Therefore, we consider that storing hair samples at refrigerated temperatures prevents degradation of DNA, allowing the detection of gene doping in these samples based on WGR. It is likely this finding will also have a deterrent effect, as it is now possible to test horses with archived samples even if they or their parents are deceased. To our knowledge, this is the first report employing WGR on horsehair roots stored for a long term.

著者

Atsushi HIRAGA Shigeru SUGANO

出版者

Japanese Society of Equine Science

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.26, no.1, pp.1-13, 2015 (Released:2015-03-31)

参考文献数

84

被引用文献数

2 8

---

Since the first recording of electrocardiograms (ECGs) of a horse in Japan was carried out in 1944, studies on ECGs have been performed intensively. During the early stages of research from the 1950s to 1960s, leads to use for ECG recording were evaluated using several different approaches including unipolar leads, bipolar limb leads, and bipolar chest leads. Based on these studies, the AB lead, which is oriented along the long axis of the heart, became the standard reference method in Japan. Electrodes of the AB lead are placed on the upper 1/4th point along a straight line between the withers and the left shoulder blade (base: B), and 10 cm posterior to the left olecranon (apex: A). The incidence of equine arrhythmias among racehorses has been surveyed, and details of the electrocardiographic characteristics of several arrhythmias have been investigated. In particular, atrial fibrillation (AF) has been extensively studied, and papers have reported findings such as that paroxysmal AF occurs during racing and described electrocardiographic changes that occur at the onset of AF during exercise. Development of a radiotelemetry system for ECG recording enabled the first recording of equine ECGs during galloping in 1964, the detection of arrhythmias, and calculation of heart rate during exercise. Studies on comparative and developmental changes of ECGs have described characteristics of the equine ECGs. Future research on changes in cardiac function, including autonomic function, that occur with aging may lead to new developments in equine electrocardiography and contribute to improving the health and welfare of the horse.

著者

Akira MATSUI Yoshinobu INOUE Yo ASAI Akira YAMANOBE

出版者

Japanese Society of Equine Science

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.16, no.1, pp.19-26, 2005 (Released:2005-04-21)

参考文献数

21

被引用文献数

1 3

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Different geographic regions in which thoroughbred yearling horses are bred have different climates and different types of forage in pasture and hay. These factors are likely to influence the energy metabolism and growth rate of yearling horses. However, the effects of the characteristics of geographic regions on the digestible energy (DE) intake and growth rate of thoroughbred yearlings has yet to be clarified in detail. Here, we have examined the effect of the breeding region on growth performance of young horses, by comparing the DE intakes and growth rates of thoroughbred yearlings in Hidaka (Hokkaido) and Miyazaki (Southern Kyushu) in Japan. Eighteen male thoroughbred yearlings were divided equally into two groups, and bred either at the Hidaka training and research center (HYF) or the Miyazaki yearling farm (MYF). Measurements were conducted in September (summer) and in February (winter), and the mean ages of the yearlings during these two periods were 18 months and 23-24 months old, respectively. The apparent digestible energy intake was measured by a double-indicator method using Cr2O3 and lignin. There was no significant difference in the DE intakes between the yearling horses at the HYF and MYF in either season. The warm land of Southwest Japan has been considered to be unsuitable for growing forage containing sufficient nutrients to feed thoroughbreds, but no nutritional disadvantage of this forage was detected in the yearlings bred at the MYF. On the other hand, the heart girth (HG) and cannon circumference (CC) were found to be significantly smaller in yearlings at the HYF, compared to those at the MYF, in the winter evaluation (p<0.05). Significant positive correlations between the ADG and DE intake/100 kg body weight were seen in animals at the HYF in the summer and in those at the MYF in both seasons; however, such a correlation was not found in horses at the HYF in winter. The reason for the smaller HG and CC and the absence of a significant correlation between the ADG and DE intake/100 kg body weight in the yearlings at the HYF in winter is unclear. It could be attributable to growth delay due to exposure to cold temperatures, or lack of supplementation to compensate for the increased energy requirement due to excess energy metabolism in cold weather. Closer attention must, therefore, be paid to the energy supply and nutritional composition of feedstuffs fed to thoroughbred yearlings at farms in regions with cold ambient temperatures.

著者

Daniel T. KASPER Rex F. GANDY

出版者

Japanese Society of Equine Science

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.29, no.3, pp.67-74, 2018 (Released:2018-09-19)

参考文献数

13

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The 2016 Equibase data set of American Quarter Horse starts in North America was analyzed, with the purpose of ranking the sires of the racehorses. A speed z-score derived from the race times and distances was used as a racing performance measure. Mixed effects models were used on various subsets of the data based on race distance and sire offspring number. The sire categorical variable was considered as a random effect. Various statistical criteria were used to optimize the model. The constructed models were then varied in terms of the random and fixed effects included, and the conditional modes of the sire effects were extracted from these models. The benefit of the sire ranking that comes from this analysis is that it is controlled for track, jockey, trainer, weather, and several other variables that can impact speed. Sires are typically valued for high rankings for offspring earnings and winners. Yet a sire with a low stud fee may still produce offspring with a high ranking using our z-score model. The offspring of this bargain sire have the potential to produce fast offspring that could pay a dividend on a relatively low cost investment. The model sire ranking approach described in this paper is clearly bringing a new approach to the field of sire rankings.

著者

Yasuyoshi MORITSU Hiromi FUNAKOSHI Shun ICHIKAWA

出版者

Japanese Society of Equine Science

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.5, no.2, pp.53-58, 1994-09-30 (Released:2010-06-28)

参考文献数

20

被引用文献数

12 17

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The sire effect and the fixed effects of sex, training center, type of course, specific racetrack, horse age and track condition were evaluated regarding best racing times of thoroughbred horses. The records of best racing times at the Japan Racing Association were collected from the electronic racing book. The data set was edited so that each sire was required to have at least twenty progeny in the racing distances of 1200m and 1800m. The total numbers o f sires and progeny were 34 and 1486 for 1200m and 34 and 1520 for 1800m. First, the least-squares analysis of variance was carried out by using the linear model which included the sire effect and the six fixed effects. Second, heritabilities for best racing times were calculated, and additionally sire evaluations were carried out by using the sire model of the BLUP method. As a result of analysis of variance, almost all effects included in the linear model were significant for both racing distances. The sire, type of course, horse age and interaction between the type of course and track condition had a highly significant effect on best racing times. Estimates of heritability were 0.11 and 0.09 for 1200 m and 1800 m, respectively. Rankings of sires' breeding values based on progeny records were quite different for the two racing distances. The Spearman rank correlation coefficient for these rankings was 0.350 (P<0.05).

著者

Teruaki TOZAKI Mio KIKUCHI Hironaga KAKOI Kei-ichi HIROTA Shun-ichi NAGATA

出版者

Japanese Society of Equine Science

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.28, no.4, pp.127-134, 2017 (Released:2017-12-12)

参考文献数

32

被引用文献数

17

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Body weight is an important trait to confirm growth and development in humans and animals. In Thoroughbred racehorses, it is measured in the postnatal, training, and racing periods to evaluate growth and training degrees. The body weight of mature Thoroughbred racehorses generally ranges from 400 to 600 kg, and this broad range is likely influenced by environmental and genetic factors. Therefore, a genome-wide association study (GWAS) using the Equine SNP70 BeadChip was performed to identify the genomic regions associated with body weight in Japanese Thoroughbred racehorses using 851 individuals. The average body weight of these horses was 473.9 kg (standard deviation: 28.0) at the age of 3, and GWAS identified statistically significant SNPs on chromosomes 3 (BIEC2_808466, P=2.32E-14), 9 (BIEC2_1105503, P=1.03E-7), 15 (BIEC2_322669, P=9.50E-6), and 18 (BIEC2_417274, P=1.44E-14), which were associated with body weight as a quantitative trait. The genomic regions on chromosomes 3, 9, 15, and 18 included ligand-dependent nuclear receptor compressor-like protein (LCORL), zinc finger and AT hook domain containing (ZFAT), tribbles pseudokinase 2 (TRIB2), and myostatin (MSTN), respectively, as candidate genes. LCORL and ZFAT are associated with withers height in horses, whereas MSTN affects muscle mass. Thus, the genomic regions identified in this study seem to affect the body weight of Thoroughbred racehorses. Although this information is useful for breeding and growth management of the horses, the production of genetically modified animals and gene doping (abuse/misuse of gene therapy) should be prohibited to maintain horse racing integrity.

著者

Hajime OHMURA James H. JONES

出版者

日本ウマ科学会

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.28, no.3, pp.99-103, 2017 (Released:2017-09-20)

参考文献数

25

被引用文献数

15

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We investigated changes in heart rate (HR) and HR variability as a function of age in newborn foals to old Thoroughbred horses. Experiments were performed on a total of 83 healthy and clinically normal Thoroughbred horses. Resting HR decreased with age from birth. The relationship between age and HR fit the equation Y=48.2X-0.129(R2=0.705); the relationship between age and HR for horses 0–7 years old fit the equation Y=44.1X-0.179(R2=0.882). Seven-day-old horses had the highest HR values (106 ± 10.3 beat/min). The low frequency (LF) and high frequency (HF) powers increased with age in newborn to old horses. These changes in HR and HR variability appear to result from the effects of ageing. Three- to seven-year-old race horses had the lowest HR values (32.9 ± 3.5 beat/min) and the highest LF and HF powers except for the HF powers in the oldest horses. Race training may have contributed to these changes. Horses of ages greater than 25 years old had the highest HF powers and the lowest LF/HF ratios. In individual horses, 8 of the 15 horses over 25 years old had LF/HF ratios of less than 1.0; their HR variability appears to be unique, and they may have a different autonomic balance than horses of younger age.

著者

Daisuke MIYAKOSHI Hiroyuki SENBA Mitsumori SHIKICHI Masaya MAEDA Ryo SHIBATA Kazuhiro MISUMI

出版者

日本ウマ科学会

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.27, no.2, pp.67-76, 2016 (Released:2016-06-21)

参考文献数

14

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This study aimed to evaluate the influence of radiographic abnormalities of 2-year-old Thoroughbred horses that were listed at in-training sales in Japan, on whether they started to race or not at 2–3 years of age. Radiographs of 850 2-year-old Thoroughbreds in the in-training sales repository from 2007 to 2010 were reviewed, and 26 categories of radiographic abnormalities were found. Forty-three horses (5.1%, 43/850) did not start a race at 2–3 years of age. In accordance with the racing results for this age category, as determined by Fisher’s exact test and multiple logistic regression analysis, none of the radiographic abnormalities were significantly related to failure to start a race. At 2 years of age, 198 horses (23.3%, 198/850) did not start a race. Horses with enlargement of the proximal sesamoid bones in the fore (9 of 19 horses) and hind limbs (5 of 9 horses) did not start a race at the age of 2 years, and fewer of these horses (fore, P=0.021; hind, P=0.030) started a race at the age of 2 years compared with the population of horses without these radiographic abnormalities. These results suggest that identification of radiographic enlargement of the proximal sesamoid bones during training sales could derail the racing debut of horses at the age of 2 years. However, this might not necessarily indicate a poor prognosis and resulting in retirement from racing at 2–3 years of age.

著者

Toshiyuki TAKAHASHI

出版者

日本ウマ科学会

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.26, no.2, pp.43-48, 2015 (Released:2015-07-02)

参考文献数

8

被引用文献数

1 17

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The running performance of Thoroughbred racehorses has been reported to peak when they are between 4 and 5 years old. However, changes in their racing speed by month or season have not been reported. The purposes of this study were to reveal the average racing speed of Thoroughbreds, and observe changes in their average speed with age. The surveyed races were flat races on turf and dirt tracks with firm or standard track conditions held by the Japan Racing Association from January 1st, 2002 to December 31st, 2010. The racing speed of each horse was calculated by dividing the race distance (m) by the horse’s final time (sec). Average speeds per month for each age and distance condition were calculated for each gender group when there were 30 or more starters per month for each age and distance condition for each gender group. The common characteristic change for all conditions was an average speed increase up until the first half of the age of 4 years old. The effect of increased carry weight on average speed was small, and average speed increased with the growth of the horse. After the latter half of the age of 4 years old, the horses’ average speed remained almost constant, with little variation. It is speculated that decreases in the weight carried; and the retirement of less well performing horses; are responsible for the maintenance of average speed.

著者

Kayo TERADA

出版者

日本ウマ科学会

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.11, no.4, pp.83-90, 2000 (Released:2001-08-16)

参考文献数

17

被引用文献数

13 52

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The aim of this study was to see if differences in proficiency exist between advanced-and novice-level horseback riders with regard to head movement and EMG activity. Three advanced-and three novice horseback riders rode a horse at a walk, sitting trot and canter whilst their head acceleration and the EMG activity of their rectus abdominis muscle (M. rectus abdominis), erector spinae muscle (M. erector spinae) and abductor magnus muscle (M. adductor magnus) were recorded simultaneously. All results were conducted with Frequency Analysis by the Maximum Entropy Method. At walk, the novice rider showed a frequency distribution dispersion (P<0.1) of the head in the proximal-distal direction which was not observed in the advanced rider, but no distinct primary factors were observed in the muscular discharge frequency distributions-perhaps due to the novice rider's level which was not completely inexperienced. At a sitting trot, unstable movements of the novice rider's upper body were observed in the cranial-caudal direction (P<0.05), mirroring the horse's violent rocking movements. The electromyogram frequency distributions at this gait suggest that the novice rider was unable to balance the erector spinae and rectus abdominis muscles, and therefore unable to cope with the unstable movement. It also suggests that there was instantaneous muscular activity of the adductor magnus muscle in order to stabilize the ill-balanced body. At a canter, there were no significant differences in the dispersion of acceleration frequency distribution or in the electromyogram frequency distribution, but although there were no "significant" differences, the results obtained from the advanced rider at this gait showed a dispersion of acceleration frequency distribution that was slightly greater than that of the novice rider. This situation was only observed at a canter. In conclusion, differences exist in the degree of difficulty of coordination between horse and rider according to the gait. In addition, from the results of this study, we can clearly see that differences also exist in the rider's own skill and ability to "maintain posture".

著者

Yusuke HORI Takatoshi OZAKI Yoshimitsu YAMADA Teruaki TOZAKI Heui-Soo KIM Ayaka TAKIMOTO Maiko ENDO Noboru MANABE Miho INOUE-MURAYAMA Kazuo FUJITA

出版者

日本ウマ科学会

雑誌

Journal of Equine Science (ISSN:13403516)

巻号頁・発行日

vol.24, no.3, pp.31-36, 2013 (Released:2013-09-30)

参考文献数

15

被引用文献数

2 11

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Genetic polymorphisms in genes related to neurotransmitters or hormones affect personality or behavioral traits in many animal species including humans. In domestic animals, the allele frequency of such genes has been reported to be different among breeds and it may account for breed differences in behavior. In this study, we investigated breed differences in horses in the dopamine receptor D4 gene (DRD4), which has been reported to affect horse personality. We collected samples from seven horse breeds including those native to Japan and Korea, and compared the sequence of the DRD4 exon3 region among these breeds. We found that there were two types of polymorphisms (VNTR and SNPs) in the exon3 region, and some of them seemed to be breed-specific. In addition, we found that the allele frequency of G292A, reported to be associated with horse personality, differed greatly between native Japanese horses and Thoroughbred horses. The frequency of the A allele which is associated with low curiosity and high vigilance, was much lower in native Japanese horses (Hokkaido, 0.03; Taishu, 0.08) than in Thoroughbreds (0.62). This difference may account for breed differences in personality or behavioral traits. Further studies of the function of these polymorphisms and their effect on behavior are indicated.