Despite growing recognition of post-race exertional heat illness (EHI) in the horse racing industry, reports on its prevalence are limited. The purpose of this study was to investigate the prevalence of post-race EHI and climate conditions at racecourses in Japan. The overall prevalence of EHI from 1999 to 2018 was 0.04% (387 cases for 975,247 starters) in races operated by the Japan Racing Association (JRA). The yearly prevalence has been increasing, exceeding 0.07% in the last four years of the studied period. The overall prevalence in summer (May–September) was 0.086% (352 cases for 409,908 starters). The monthly prevalence varied among the 10 JRA racecourses, which are distributed from latitude 34 to 43°N, ranging from no cases to 0.459%. During summer, prevalence of post-race EHI was high when the mean monthly ambient temperature was high at a racecourse. To evaluate climate conditions, we investigated the wet-bulb globe temperature (WBGT, °C) from 9 AM to 5 PM on sunny race days in July and August of 2017 and 2018 at three racecourses with a high prevalence of EHI among the 10 racecourses. The durations of time during which WBGT was between 28 and 33°C at these three courses were 95, 94, and 65% of the minutes measured, respectively. This result indicated that most races on the sunny summer days were held when WBGT was between 28 and 33°C at the three racecourses. These findings could be useful in developing the appropriate countermeasures to be taken during hot weather at each of the studied racecourses.

This study compares clinical characteristics between induction with thiopental/guaifenesin and propofol/ketamine in Thoroughbred racehorses anesthetized with sevoflurane and medetomidine. Clinical records of 214 horses that underwent arthroscopic surgery between 2015 and 2016 were retrospectively retrieved. Horses were premedicated with medetomidine and midazolam to sedate at the adequate level for smooth induction, and then induced with either thiopental (4.0 mg/kg) and guaifenesin (100 mg/kg) in Group TG (n=91) or propofol (1.0 mg/kg) and ketamine (1.0 mg/kg) in Group PK (n=123). Anesthesia was maintained using sevoflurane with constant rate infusion of medetomidine. Quality of induction/recovery, sevoflurane requirement, cardiovascular function and recovery characteristics were evaluated. Anesthetic induction scores (median, range) for Group TG (5, 2–5) and Group PK (5, 2–5) were not significantly different. There were no significant differences in end-tidal sevoflurane concentration (mean ± standard deviation) between Group TG and Group PK (both 2.4 ± 0.2%). Dobutamine infusion rate (µg/kg/min) required for keeping mean arterial blood pressure (MAP) above 70 mmHg in Group PK (0.43, 0.10–1.40) was significantly lower than in Group TG (0.67, 0.08–1.56). Recovery score in Group PK (5, 2–5) was significantly higher than in Group TG (4, 2–5). Both propofol/ketamine and thiopental/guaifenesin provided a smooth induction of anesthesia. Moreover, induction with propofol/ketamine resulted in lower dobutamine requirements for keeping MAP above 70 mmHg during maintenance, and better quality of recovery. Induction with propofol/ketamine would be preferable to thiopental/guaifenesin in Thoroughbred racehorses anesthetized with sevoflurane and medetomidine during arthroscopic surgery.

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.

Twelve Thoroughbred racehorses were diagnosed as epiglottic entrapment at the Korea Racing Authority equine hospital. Four different surgical correction techniques were used to treat epiglottic entrapment: the transnasal hook bistoury, transoral unshielded hook bistoury, transnasal shielded hook bistoury, and transendoscopic laser techniques. Eleven cases were surgically resolved eventually, with one case of recurrence. Five complications related to surgical correction occurred: a severe nasal passage laceration and bleeding (n=1), epiglottic laceration (n=1), epiglottis tip burns (n=2), and moderate nasal passage laceration (n=1). Intraoperative complications occurred in approximately 41.7% of cases. Thus, the possibility of surgical complication should be considered thoroughly when choosing a surgical technique for correction of epiglottic entrapment.