• Journal of Veterinary Clinics
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• v.15 no.2
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• pp.358-363
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• 1998

These studies were performed to investigate what genital diseases could be diagnosed by ultrasonography in the mares associated with infertility. Of 159 thoroughbred breeders(4 to 18 years old), 31 mares which had been considered as the mares with reproductive disorders were examined by ultrasonography during the breeding season. 1. Hematoma in ovarian disordersl endometritis and pyometra in uterine disorders could be diagnosed by ultrasonography. 2.The rate of infertility was 19.5% out of 159 breeders and the rate of uterine disordres was 71.0% among the whole reproductive disorders. 3.Of 31 mares considered as the mares with infertilityi 26 mares were diagnosed by ultrasonography denoting 83.9% of diagnosis rate. 4.The highest average age of mares among the mares with reproductive disorders was 11.7 years in the mares with uterine disorders. The average age of the mares diagnosed as concepted was 7.5 years, which was much lower than that of the mares with reproductive disorders.5.Crushing one of twin vesicles was confirmed by ultrasonography. In conclusions ultrasonography was feasible for diagnosis of the mares with reproductive problems.

• Journal of Embryo Transfer
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• v.11 no.1
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• pp.85-91
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• 1996

Plasma progesterone concentrations were measured by using radjoimmunoassay for early diagnosis of pregnancy in Cheju-native mares. A total of 226 pony mares were examined for pregnancy during breeding and non breeding seasons. Plasma progesterone levels 20~23 days after the onset of oestrus were 4.67+O.67ng /rnl and O.55+O.O4ng /ml for mares becornrning pregnant and not pregnant after the estrus, respectively, and there was a significant differences (p<0.01) between the two groups. Progesterone concentration of pregnant mares gradually increased in 30 days andreached a peak (10.3ng /ml) during the third month of gestation. However, the concentration decresed to the base line (1.llng /rnl) at 7 months and gradually increased again as foaling approached (2.lng /ml). Early diagnosis for pregnancy of Cheju mares by progesterone level at 20~23 days after onset of oestrus was 88% accurate when 4.6ng /ml was used to classify mares as pregnancy and below 1.3ng /rnl was used to determine nonpregnant mares. However, the accuracy of the diagnosis was improved to 96% when a progesterone level of above 2ng /mi was used to classify mares for pregnancy. Diagnosis for pregnancy was 69.6% accurate when mares were classified as pregnancy by horse owners during breeding season. The progesterone levels of pregnant and non-pregnant mares during non-breeding season varied greatly between individual animals, Plasma progesterone levels of pregnant animals ranged from 3.5ng /mi to above 6.2ng /mi whereas similar values were observed in non-pregnant animals. Radioirnrnunoassay technicjues can be applied for the early pregnant diagnosis of Cheju native mares when progesterone levels are measured during the early gestation period (18~23 days after onset of oestrus). However, progesterone concentration of mares in non-breeding season is conisidered unsuitable as a indicator of pregnant diagnosis.

• Asian-Australasian Journal of Animal Sciences
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• v.27 no.7
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• pp.932-936
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• 2014

Breeding records of 57 Arabian and 66 Thoroughbred mares were analysed to assess their reproductive performance under the subtropical conditions of Pakistan. The Arabian mares showed significantly higher conception rates (p<0.05) in second mated oestrus and foal heat mated oestrus compared to Thoroughbred mares. However, conception rates for first lifetime mated oestrus were similar in both breeds of mares. Age at first mating ($1,301{\pm}40$ vs $1,500{\pm}32$ days) was significantly (p<0.05) less in Arabian compared to Thoroughbred mares. Both breeds of mares showed significantly (p<0.05) higher frequencies of oestrous cycles and conception rates during the winter (October to March) compared to summer (June to August) months. Age of mares affected the conception rates, as mares at ages 3 to 7 and 8 to 12 years of ages had significantly higher conception rates (p<0.05) than those ${\geq}18$ years old in both breeds. This study demonstrates that i) reproductive performance in Arabians is better than Thoroughbred mares under the subtropical conditions of Pakistan, ii) mares remain cyclic throughout the year and iii) conception rates were higher in mares bred during winter compared to summer months.

• Animal cells and systems
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• v.6 no.4
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• pp.293-299
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• 2002

We investigated seasonal variation of diurnal activity patterns in Jeiu ponies (Equus caballus). The data were collected from a semi-natural herd during daylight hours from March to September 1998. Over all months the mean proportion of time spent grazing was 83.7% ( $\pm$29.7 S.D.): that resting was 15.7$\pm$17%, grooming 0.7$\pm$1.2%, and moving 0.56$\pm$5.4%, Activity patterns varied with the seasons. The mean proportion of grazing mares peaked during late winter and early spring (March), when there was not enough food, and declined during other seasons (between May and September), when food was abundant. The mean proportion of mares that were resting and mutual grooming peaked in spring (April and May), at which time the weather was warm and food became abundant. During other seasons when grasses started to grow and the weather was mildly cool, these activities were less common. The mean proportion of mares that were moving peaked in June, although it was a small proportion of the total activity. For those mares without foals, resting periods were longer in older mares than in younger mares, but for the mares with foals this pattern was not evident. From these data, we hypothesize that the dominance hierarchy of the mares effects the diurnal activity pattern.

• Journal of Animal Science and Technology
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• v.64 no.1
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• pp.1-9
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• 2022

Equilume light masks had no impact on hastening the resumption of estrous cyclicity in mares maintained in outdoor pastures on the mainland of Korea due to the cold weather conditions. Jeju Island is a major horse-breeding site in Korea and is warmer than the mainland during the winter season. Therefore, the primary objective of this study was to explore the efficiency of the Equilume light mask on the resumption of seasonal estrous cycles in Thoroughbred mares on Jeju Island. A total of 20 nonpregnant mares were randomly divided into the Equilume light mask (n = 9) and stable lighting (n =11) groups. The experiment was performed at seven different horse-breeding farms located on Jeju Island from November 15, 2020, to February 15, 2021. The mares were exposed to the respective lights from 16:00 to 23:00. Follicle size and uterine edema were measured by ultrasound scanning. Body condition scores (BCS) were also monitored during the experiment. Statistical analysis was conducted using the SAS and SPSS software, and p-values of < 0.05 were considered statistically significant. Two of the nine (22.2%) mares in the Equilume light mask group and three of the 11 (27.28%) mares in the stable lighting group were still cycling in December and January, which were considered as all-year-round cycling mares. On February 15, there was no difference between groups in the resumption of early seasonal estrus cycle, which was determined by follicles > 25 mm in addition to uterine edema. All mares in the Equilume light mask group and five of the eight mares (62.5%) in the stable lighting group had resumed cycling. Interestingly, six of the seven mares (87.5%) in the Equilume light mask and four of eight mares (50%) in the stable lighting group had already ovulated on February 15 (p > 0.05), as determined by the presence of a recent corpus luteum. No difference was observed in BCS and uterine edema between groups (p > 0.05). In conclusion, the Equilume light mask can be an effective approach to induce early seasonal estrus cycles of mares in Jeju Island, and it also enhances the efficiency of farm management by reducing labor.

• Animal cells and systems
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• v.7 no.2
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• pp.119-122
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• 2003

In order to determine whether foals of move dominant mothers were harassed less by mares than those of lower-ranked mothers, harassment of foals was studied in a herd of Jeju ponies (Equus caballus) consisting of 73 mares, their 53 foals, and one stallion. Mares Harassed the foals on 71 occasions between March to September,1998. The frequency of harassment tended to decrease as foals aged, but the relationship was not significant (P = 0.079). Foals were harassed when sleeping (n = 14), grazing (n = 19), moving (n = 8), approaching a mare in the vicinity (n = 13), or play-fighting with the foal of the harassing mare (n = 17). Mares harassed foals of younger, more subordinate mares than those of older, more dominant mares (P < 0.001). We conclude that early social experience of foals is associated with the dominance rank of its mother.

• Journal of Animal Science and Technology
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• v.54 no.3
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• pp.165-174
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• 2012

For horse breeders or managers, it is critical to understand the estrous cycle of mares. Breeding of mares cannot be successfully achieved throughout the whole year as mares breed seasonally. Mares are only able to breed when day length is more than 16 h, and this period is known as the breeding season. Their estrous cycle is approximately 21 days with 5-7 days of estrus and 14 to 15 days of a diestrus period. The estrous cycle of the mare is mainly controlled by gonadotropins, which control follicular development and ovulation. Mares exhibit unique ovulatory events which are not observed in other species. A LH surge occurs for several days, with levels of LH reaching their peak after ovulation. The LH level at the time of LH peak is lower than most other species. The unique anatomical structure of the ovaries of mares is known to limit the number of eggs ovulated. Several attempts have been made to develop chemical/hormonal agents which might be used to manipulate the timed ovulation of mares. Agents that have been tested include hCG, native GnRH, Deslorelin (Ovuplant, GnRH-agonist), Buserelin (GnRH analogue), equine pituitary extracts and equine chorionic gonadotropin (eCG or PMSG). However, the function, purity or stability of these agents is not reliable. Recombinant equine LH, an alternative agent for the timed ovulation, has been developed and tested for its biological activities, through the use of both in vitro and in vivo experiments. The reLH was suggested to be a reliable agent in inducing ovulation within 48 h after being administered through injection, when the size of dominant follicle is 35 mm in diameter.

• Journal of Animal Reproduction and Biotechnology
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• v.35 no.2
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• pp.171-176
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• 2020

Advancing the estrous cycle of mares is an essential breeding strategy that is routinely conducted by Thoroughbred breeders to improve economic outcomes. For this purpose, Equilume light masks have been developed as an alternative to existing technologies such as artificial lighting or hormonal treatments because they are considered as valid as existing methods with additional animal welfare advantages. For example, with the Equilume light masks, horses can be let out into the pasture, whereas they have to be kept indoors during lighting treatment. Because the function of Equilume light mask on the estrous cycle of mares is influenced by environmental factors such as nutrition condition and temperature, Equilume light mask should be studied in various environments. The objective of the present study was thus to verify the effect of Equilume light masks on the onset of the estrous cycle in Thoroughbred mares in South Korea. Mares were randomly selected and separated into two groups at two Thoroughbred horse breeding farms. The mares in the treatment group were equipped with Equilume light masks from November 18 to February 10 the following year. The body condition, the number and size (> 35 mm) of uterine follicles, and the uterine horn score of the mares were assessed on January 6 and February 10. The body condition scores were not different between the two groups. The treatment with the Equilume light mask had no positive effects on developing follicles and the reproductive tract. In conclusion, the use of Equilume light masks did not influence the seasonal resumption of the estrus cycles in Thoroughbred mares in South Korea.

• Journal of Veterinary Clinics
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• v.15 no.1
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• pp.22-29
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• 1998

To investigate the estrual changes of ovaries, appropriate time of mating, diagnosis of early pregnancy after mating, and diagnosis of twin fetuses, ultrasonography was performed in 61 thorough-bred mares (5-12 years old) which had been raised in Chrju island. The followings are the results obtained: 1. The average size of a follicle of mares was $3.2{\times} 3.8cm$ at the beginning of estrus and $4.2{\times} 3.5 cm$ from the middle of estrus to ovulations respectively, and the average size of a follicle and a corpus luteum was $1.8{\times} 1.4 cm and 3.1{\times}2.3 cm$ in the middle of diestrus, respectively. 2. In the result of pregnancy according to mating time after ultrasonographic examination of follicle size, the mares having a follicle of 4.6-5.0 cm (diameter) were mated on the day of ultrasonographic examination or the next day rind all were conceived (3 mares) and another mares having a follicle of 4.1- 4.5cm (diameter) on the 1st or 2nd day after examination and all were conceived (4 mares). 3. By ultrasonographyi early pregnancy in the mares was diagnosed from 12 days of pregnancy and the equine fetus was directly detectable from 23 days of pregnancy, whereas the heartbeat of a fetus was detectable from 28 days of pregnancy. 4. Diagnosis of earl pregnancy of twin was possible from 16 days of pregnancy. These result indicated that ultrasonography is applicable in mares to diagnose the estrual changes of ovaries and the time of ovulation or mating, and to diagnose early pregnancy from 12 days of pregnancy and early pregnancy of twin fetuses.

• Korean Journal of Veterinary Research
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• v.44 no.1
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• pp.105-111
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• 2004

A total of 301 Thoroughbred mares were investigated the characteristics of breeding in the local areas in Jeju during the period from February 2000 to July 2001. The pregnancy rate and foaling rate in 143 mares were 93.0%, 72.0%, respectively, and mean gestational length was 339.3 days in 2000. The pregnancy rate in 158 mares was 86.7% in 2001. Mature follicles were ovulated in right(46.0%), left(45.2%), and bilateral(7.8%) ovary. The incidence of multiple pregnancies in 158 mares between 15 days and 45 days after mating were 89.3%(single), 10.1%(twin), and 0.6%(triple). The incidence of EED was 13.3%. Also uterine cyst and fluid had an bad influence on mare's pregnancy. These results suggest that regular monitoring of the pregnancies and maintaining of good uterine condition improve the pregnancy rates and foaling rates during breeding season.