Most of the bone fractures in racehorses occur in the fore limb, especially in the metacarpal joint during the racing and training. The longitudinal fracture of the third metacarpal bone (Mc III) often occurs in the osteosclerotic and/or necrotic lesions in the distal part of the bone. To elucidate the endogenous factors of its fracture, soft radiograms of 4 fractured and 4 non-fractured control cases have been investigated morphometrically by a image anaryzer. In addition, to analyze the quality of these bones, 20 elements of mineral contents in the crashed bones have been measured using a fluorescent X-ray analyzer. As the results, the osteosclerotic change was observed in both groups in the plantar side of the distal part of Mc III, however, no significant differences were found in the bone morphometry. No significant differences in the 19 elements of bone mineral contents were found except Fe. From these findings, the mechanism of the occurence of the longitudinal fracture in the Mc III remains to be elucidated. In future, further work needs to be done with regard to the mechanical intensity and collagen disposition of the distal part of the Mc III.

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One of the digital radiography systems, the Computed Radiography (CR) system (Fuji Computed Radiography CR-201^®, Fuji Photo Film Co., Ltd. Tokyo) using photostimulable phosphor has been newly developed in Japan. In this study, we estimated how this equipment was useful as a novel method on X-ray diagnosis in equine veterinary practice. And then, we studied how much X-ray dose was decreased by using the CR system in our daily examinations with a portable X-ray tube which is used for most X-ray diagnosing of racehorses. Also, we compared the X-ray image quality between the CR system and conventional one in some clinical cases. As a result, it was found that, by using the CR system, direct X-ray dose could be decreased to less than 25% and scattering X-ray dose diminished to 1/10-1/20 of those in the conventional method. In addition, the CR images proved clinically to be better in density, sharpness and contrast compared with the conventional images. From these findings, it was suggested that this equipment was useful enough to X-ray diagnosis in equine veterinary practice.

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One of the digital radiography system, the Computed Radiography (CR) system (Fuji Computed Radiography CR-201^®, Fuji Photo Film Co., Ltd. Tokyo) using photostimurable phosphor has been newly developed in Japan. In this study, we estimated how two functions among several image processing function in this equipment, the superimposed and subtracted image-processing functions, were useful on X-ray diagnosis in equine veterinary practice. And then, we studied the usefulness of the superimposed image-processing function on diagnosis by using a high potential X-ray tube and of the subtracted image-processing function in elective angiography with intra-arterial injections. As a result, it was found that superimposed image-processing function was effective enough for reducing the X-ray dose, or for photography under the conditions of low X-ray tube voltage and short exposure time. By using this function, we could avoid an unclear image caused by the horse's movement by shortening the exposure time and the amount of scattering X-ray dose was also decreased by lowering the X-ray tube voltage. In addition, it was found that, by using the subtracted image-processing function, diagnostic value of angiogram could be improved and lower concentration of contrast medium could be used.

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Neutralization test (NT) was conducted for detection of neutralizing antibody against calf diarrheal coronavirus (CDCV) for application to serological survey among horses. The plaque-reduction neutralization test (PRNT) and the micro-titer neutralization test (MTNT) were examined with Kakegawa strain of CDCV and HmLu-1 (humstar lung) cells. The specific serum neutralizing antibody detected by PRNT and MTNT developed at the same rate with the PRNT titer being higher than the MTNT titer in the sera of two horses experimentally inoculated with CDCV. To know the difference of the antibody titers detected by both neutralization tests, both serum neutralization tests were performed in serum samples of 100 racehorses. Consequently, 40 samples were negative (less than 5) in both tests, 19 samples were positive (5 or more than 5) by PRNT and negative by MTNT and remaining 41 samples were positive for both tests. The titers detected by both tests were closely correlated with each other, although neutralizing antibody titers detected by PRNT were higher in the order of 2 to 16-fold than those detected by MTNT. According to the serological survey by MTNT, 3 to 60% horses in rearing farms and 52% horses in breeding farms possessed the neutralizing antibody against CDCV, respectively. From these results, it was demonstrated that a viral agent antigenically related with CDCV existed widely among horses in Japan.

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Twenty-eight monoclonal antibodies (MoAbs) specific for equine herpesvirus 1 (EHV-1) were established. Of these MoAbs, 15 were specific for two different subtypes of EHV-1, while the remaining were cross-reacted with both subtypes. In addition, 10 of these MoAbs were examined for further immunological characterization and for their use in subtyping. The subtyping was checked against the already subtyped 8 field isolates with the results indicating that these MoAbs were useful for subtyping of EHV-1.

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A Thoroughbred brood mare, 18 years and 11 months of age, contracted chronic canker in both front hooves. A foul-smelling exudate and a light gray, brushlike vegetative growth issued from the white line and the wall of both affected hooves. The main body of the vegetative growth was a proliferation of the stratum lamellatum and corium of the hoof wall. Histopathological findings included proliferation and hypokeratosis of the epidermal lamellae, associated with necrosis, and balloon degeneration of the epidermal cells. The corium was characterized sporadically by fibrous hyperplasia, extreme inflammatory changes and edema, cell infiltration, hydropic vacuolation and intimal fibrosis of the small and medium arterial walls, and vascular stenosis. Blood circulation within the corium, which provides nutrition to the epidermal lamellae, had been impaired by chronic edema, and this was deduced to be a likely factor contributing to the hypokeratosis of the epidermal lamellae.

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