This study observed the fluctuation of total hemoglobin (tHb) and reduced hemoglobin (dHb) concentrations as a direct reflection of hemodynamics under the hoof wall with near infrared spectroscopy (NIRS). NIRS observation of the laminar layer under the pigmented hoof walls was performed without sedation or invasion on five clinically normal horses. NIRS indexes relating to the concentration change of tHb (tHbindex) and dHb (dHbindex) in tissue were recorded at 2 Hz and evaluated over 0.004 Hz in spectral power. Each NIRS index fluctuated spontaneously and continuously from 0.01 Hz to 0.05 Hz. Over 10 times difference of total power was shown in fluctuations of each NIRS index. Nevertheless, a significant positive correlation was observed between NIRS indexes. In the geometrical distribution of the power spectra from 0.0078 Hz to 0.5 Hz, the sub-band power of the dHbindex dominated the tHbindex in sub-bands with central frequencies of 0.011 Hz and 0.022 Hz. This was interpreted as characteristic of the hemoglobin oxidation-reduction (redox) fluctuation common to forelegs of both sides. NIRS observation based on the second time scale and adapted by spectral analysis was able to evaluate qualitatively the characteristics of spontaneous kinetics of hemoglobin redox regardless of a lack of quantity, suggesting the ability to provide virginal vital signs under hooves.
The incidence of Bider (Bi marking) in Mongolian native horses was 0.010, and that according to districts was the highest (0.032) in Tov Aimag. Bi marking was frequently observed in bay (0.482) and chestnut horses (0.351), and was also observed in gray and roan horses. The incidence of Bi marking was high (0.842) in horses with a dorsal strip (DS) as a primitive marking. In 164 Equus przewalskii, the incidence of Bi marking was 0.396, which was about 40 times the incidence in Mongolian native horses. Bi marking was observed in both males and females in the two species, showing autosomal inheritance. Analysis of the mode of inheritance based on the incidence of Bi marking in foals according to various crossing combinations showed the complete dominance of Bi marking in both species. Thus, it was concluded that Bi marking occurs in Bi/Bi and Bi/- genotypes. This Bi marking differs from DS, leg stripes (LS) and shoulder stripes (SS), and is considered to be a type of primitive marking peculiarly occurring in Mongolian native horse and Equus przewalskii. The high incidence of Bi marking in Equus przewalskii (0.396), and the results of crossing between Mongolian native horses and Equus przewalskii performed in Mongolia, suggest introgression of the Bi marking gene from Equus przewalskii to Mongolian native horses.
We measured the heart rate before, during and after a 1200-m race, and blood lactate concentration at 10 min after a race in 23 Thoroughbred horses. The heart rate increased when horses were walking through the underground passage and after the jockeys mounted them in the paddock, even though there was no increase in exercise intensity. During the canter from the exit of the underground passage to the starting stalls, the heart rate increased to a peak value of 194.0 ± 2.0 (mean ± SE) beat/min, which was equivalent to 91.1 ± 0.8% of the maximal racing heart rate. In the starting stalls immediately before the start of the race, the heart rate was 171.4 ± 5.3 beat/min. The peak value of the heart rate (HRpeak) during the race was 213.6 ± 1.7 beat/min, and the time taken to reach 95% of HRpeak was 12.4 ± 1.8 sec. The blood lactate concentration after the race was 22.5 ± 0.6 mmol/l. The mean speed of the horses was 15.9 ± 0.0 m/s, which was similar to those of 3-year-olds in maiden races. These data could be useful for planning training strategies for Thoroughbred horses.
TA and BALF obtained from 44 Thoroughbred racehorses that developed pneumonia after long-distance transportation were examined cytologically and bacteriologically. The percentages of neutrophils in both TA and BALF collected from the same horses at the same time were almost the same and were very high indicating inflammation. Various bacteria, including obligative anaerobius which are categorized as opportunistic pathogens, were isolated from BALF, and the bacteria isolated mainly in the later stages of the clinical course tended to be resistant to cephalotine and gentamicin, which are used as the first choice in the racehorse hospital of JRA where this study was performed.