Calcium, copper and zinc contents in the pasture grass and the incidence of epiphysitis of the fetlock joint were surveyed on the breeding farms in the western, central and eastern area in Hidaka district, Hokkaido, Japan. 25 farms and 278 foals were used in this study.
The averages of calcium, copper and zinc contents were 0.363%, 7.08ppm and 26.4ppm respectively, and they were lower than the contents of feed composition tables on NRC. Copper contents in the central area was significantly lower than those in other areas. The incidence of epiphysitis of the fetlock joint was 23.0% (64 foals) and their ages ranged from 100-200 days old. The incidence of epiphysitis of the fetlock joint in the foals grown at the pastures in which copper contents were lower was 34.3%, it was significantly higher than others. But there were no relationships in the cases of calcium and zinc.

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The objective of the present study was to evaluate the training effect from daily heart rate during warming up (W-up). Five 2-year-old Thoroughbred horses (2 colts, 3 fillies) were used. These horses were trained for four months, six days a week. And we measured heart rate during daily W-up.
Rider received instructions to run 1, 250m at a speed of 400m/min during W-up. Heart rate during W-up were analyzed using 5-day moving average method.
The heart rate decreased gradually from the beginning of training to about sixty days and then remained at the same level. And we measured V₂₀₀ and V₁₇₅ (running speed at heart rate 200 and 175 beats/min) during standardized exercise test every two weeks.
There were significant correlations between mean heart rate during W-up and V₂₀₀ of standardized exercise test. (r=0.765, P<0.001) Therefore, we considered that it is possible to evaluate the training effect from the change of low heart rate during daily W-up.

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Thirteen strains of Rhodococcus equi from 12 independent clinical cases were analyzed for the presence of virulence plasmid DNA. Of the clinical isolates except strain JRA-11, 10 contained an 85-kb virulence plasmid and the remaining 2 contained a 90-kb virulence plasmid. The twelve isolates expressed 15- to 17-kDa antigens and were virulent in mice. Strain JRA-11 contained no plasmid and was avirulent in mice. These strains were examined by Southern analysis with pREAT 701 plasmid probes, and their plasmid DNAs were hybridized with the probes. These results revealed that natural infections in foals could be principally caused by virulent R. equi, but not by avirulent organisms.

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Horse skeletal muscle myosin was isolated from nine distinct muscles; transverse pectoral, gluteus medius, extensor carpi radialis, gastrocnemius, descending pectoral, internal intercostal, longus coli, diaphragm and masseter.
The light and heavy chain subunits of myosin were focused on to determine their predisposition to associate with fast or slow twitch fibers and the impact of their specific distribution.
A 15% SDS separating gel in Tris buffer was used for light chain, and for heavy chain study 5% gels with 25% glycerol. Proteins were quantitated with a laser-beam densitometer (LKB) connected to a computer programmed integrator.
The result showed that extensor carpi radialis and gastrocnemius were typical fast twitch muscles, as evidence by the preponderance of fast-twitch fibers in heavy chains (>90% HC_f) and light chains (100% LC_1f+LC_2f). Descending pectoral (D. P.) and internal intercostal (I. I.) can be classified as intermediate with a much greater content of fast-twitch light chains LC_1f and LC_2f, than of slow-twitch light chains LC_1s and LC_2s. The masseter can be classified as typical slow-twitch muscle on the basis of light and heavy chain composition. Longus coilli and diaphragm were also intermediate with respect to light chain composition, containing LC_1s and its isoform and LC_2s as well as LC_1f, however, heavy chains comprised only slow-twitch fibers (100% HC_s). Internal intercostal, extensor carpi radialis and diaphragm contain an isoform of LC_1s. Both I. I. and D. P. contain almost equal portions of HC_f, and HC_s. The transverse pectoral and gluteus medius can be classified as fast-twitch muscle on the basis of the predominance of the LC_1f and LC_2f subunits and the appearance of detectable amounts of LC_3f. Almost 100% of the 2 heavy chains in these muscles were HC_f. The diversity found in chain distribution among skeletal muscle myosin from a single horse was unexpected.

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Respiration pause and gait after the start dash from the starting gate was described by respiration curve, acceleration curve of forelimbs and high speed photograph in a healthy horse. The respiration pause was observed for 3 and 4 seconds immediately after two dashes, during an inspiratory phase following an expiratory phase. The respiration was generated to way to acceleration of speed and synchronized immediately with the stride. Also, when the respiration pause was observed, the horse used a rotary gallop or changed the lead before settling into a transverse gallop. Therefore, it was considered that the respiration is inhibited temporarily by maximal effort run such as start dash and the respiration pause is not related to the gait and lead change.

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In order to investigate whether transport does have influence on white blood cells count in the peripheral blood in racehorses, clinically healthy 337 thoroughbred racehorses were examined hematologically prior to and immediately after transportation.
There was a tendency to increase in the number of leukocyte after transportation. The increase was mainly due to neutrophilia. It would appear that leukocytosis might have originated from the stress associated with transportation. The causal factor of leukocytosis remains to be studied.

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An attempt was made to develop a complement fixation (CF) test for equine viral arteritis (EVA) which can be safely used in the countries free from EVA. The antigen was inactivated by 0.1% formalin, 50% ether, ultraviolet (UV) irradiation and heat at 70°C respectively. It was efficiently affected in viral infectivities by ether and formalin, but not at all in CF titers by formalin and UV irradiation. Ether degraded CF titers readily and UV irradiation caused random inactivation of virus. Heat showed incomplete effect on viral infectivities and declined CF titers. Therefore, the antigen inactivated by formalin was selected in the subsequent CF studies.
To evaluate the CF test using the inactivated viral antigen, it was conducted with 6 sero-positive horse sera against EAV in serum neutralization (SN) test. Three sera possessing SN titers of 1:128 to 1:256 revealed titers of 1:4 to 1:8 in CF test. The rest which had SN titers of less than 1:64 were negative.

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A serological survey of Lyme borreliosis in horses in Japan was conducted with the immunofluorescent antibody (IFA) test and fluorescent enzyme-linked immunosorbent assay (fluorescent ELISA). Of 700 horse sera, mostly from draught horses from 14 districts of Hokkaido, 32 (4.6%) had positive IFA titers of ≥1:32. Of the 14 districts, higher positive antibody rates were detected in the 4 districts of Kushiro, Tokachi, Abashiri and Kamikawa compared to the other districts. The sera from these 4 districts were examined with fluorescent ELISA and the antibody titers were expressed as the relative fluorescent signal (%RS). The %RS values were compared with IFA titers in each sera. Cutoff points for positive antibody were set as 1:32 for IFA and 2 for %RS of fluorescent ELISA. Of 549 sera from light horses from different localities of Japan, 14 (2.6%), were positive by a fluorescent ELISA.

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