This report describes the descriptive epidemiology of racing fractures that occurred from
the 1980s to 2000s on racetracks of the Japan Racing Association (JRA). The incidence of
racehorse fractures during flat racing was approximately 1–2%. Fractures occurring during
a race are more likely to occur in a forelimb. Fractures mostly occur at the third and
fourth corners of oval tracks and on the home stretch. They also occur more frequently at
the time of changing the leading limb. Comparison of the incidence of racing fracture
between before and after reconstruction of the geometrical configuration of a racetrack
revealed that there was an outstanding reduction in the number of serious fractures in the
year before and after reconstruction. It was postulated that the improvement in racing
time, possibly influenced by reconstructing the geometrical configuration of the
racetrack, was connected to the reduction in the number of fractures. Of non-biological
race- and course-related factors, type of course (dirt or turf), track surface condition,
differences between racecourses, and racing distance significantly influence racing time.
By using an instrumented shoe, vertical ground reaction forces (VGRFs) on the forelimb
during galloping and the relationships between a rough dirt and woodchip track surface and
a smooth dirt and woodchip surface were measured. Relating the incidence of racing
fractures with track conditions in general showed that track surface has significant
effects on the incidence of fracture, with the incidence of fractures increasing as track
conditions on dirt worsen and a tendency for the incidence of fractures to decrease as
track conditions on turf worsen. It seems probable that track condition in general may
affect the incidence of fracture. The incidence of fracture in horses during both racing
and training decreased as the years progressed.
Uteri from 50 necropsied nonpregnant Japanese Thoroughbred brood mares (1–30 years of age) were investigated to clarify the
histopathological characteristics of endometrosis in Japanese Thoroughbred mares and the distribution pattern of endometrosis
lesions in the uterus as a whole. Endometrosis was observed in all animals over 6 years of age and in all of the 21 mares aged
over 12 years of age. The affected mares showed elastofibrosis of arteries, veins and lymphatic vessels in the uterine wall,
atrophy of the uterine smooth muscle layers and hyperplasia of collagen fibers among the smooth muscle fascicles of the
myometrium, in addition to pathomorphologic features of endometrosis such as stromal endometrial fibrosis accompanied by
endometrial atrophy, periglandular fibrosis and reduction of uterine glands. The severity of the histopathological changes
increased with advancing age. Lymphatic vessels with elastofibrosis showed marked lymph congestion, leading to lymphatic edema.
With increasing age, the extent of the distribution of these lesions tended to expand from focal to diffuse involvement of the
entire uterus. Based on these findings, we speculate that aging plays a role in the pathogenesis of endometrosis; circulatory
disturbances due to intrauterine angiosis or angiopathy, particularly reduction of the arterial blood supply and disturbance of
venous drainage, resulting in a reduction of lymphatic drainage (lymphatic edema), are closely related to the onset and
progression of endometrial fibrosis and myometrial atrophy with fibroplasia may result in myometrial hypofunction during the
peri-implantation or puerperal period.
The secretions of the equine endometrial glands are essential for the survival, growth,
and development of the conceptus in early pregnancy, and endometrial gland density is
directly related to successful pregnancy outcome. Endometrial biopsy is routinely used to
assess the reproductive potential of broodmares. Some previous studies have shown that
equine endometrial glands are uniformly distributed throughout the uterus; however, other
work has shown variation of the endometrial architecture between biopsy sites, suggesting
that a single biopsy is not representative of the entire endometrium. The aims of this
study were to assess and compare the endometrial gland density and thickness at four
sampling sites in the uterus (the central segment of each uterine horn, the uterine
horn-body junction, and the caudal portion of the uterine body). Endometrial samples from
five nulliparous Thoroughbred mares in diestrus were obtained at necropsy and used for
subsequent histomorphometric analysis. The caudal uterine body had a significantly lower
endometrial gland density and endometrial thickness than the other sites. This may result
in nutrient deprivation and reduced survival of embryos or fetuses in this region of the
uterus. The endometrial gland density and endometrial thickness did not significantly
differ between the other regions sampled, indicating that they are similarly suitable for
embryonic implantation and fetal development. Our results suggest that the endometrial
structure of the caudal uterine body of the mare is not representative of the endometrial
morphology at other sites. Thus, the caudal uterine body is not a suitable site for
routine endometrial biopsy.
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