Although the total number of horses raised in Japan dramatically decreased after World War II, because draft horses were still used for farm work in paddy fields and on farms during the period of the 1950s and 1960s, a performance test for selecting better draft horses was needed. In order to determine the most suitable size of draft horses for Japanese farm conditions, the working power of horses weighing from 185 to 622 kg was evaluated by performing an endurance test, several kinds of working power tests, and maximum pulling power tests. Oxygen consumption during draft exercise was measured by the Douglas bag method in order to evaluate effects of draft workload under the conditions of different types of work (14- and 18-cm plow depths, cultivator, and tillage), traction methods (shoulder traction, shoulder-trunk traction, and chest-trunk traction), walking speeds (40, 60, 80, 100, and 120 m/min), and depths of water (0, 18, 36, and 54 cm) on energy expenditure. The relationship between energy consumption and pulse rate during exercise was also evaluated. A study of a performance test for draft horses was conducted to establish a new approach for evaluating draft horse performance using heart rate as an index. For this study, a beat meter for measuring heart rate was developed, and experimental protocols were used to evaluate the relationship between heart rate and workload. Although the research results obtained from these studies do not have particular relevance in the current day, these studies are valuable for understanding the history of equine exercise physiology in Japan.

Global positioning system (GPS) units are now lightweight and compact. They have proven useful for analyzing the behavioral characteristics of horses in pastures. Because the GPS records data in latitude and longitude, it may be feasible to calculate the distance between GPS units. The present study aimed to confirm the applicability of GPS units in behavioral studies on horses. For this, we analyzed the accuracy of the distances calculated from GPS units using Hubeny’s distance formula and of the monthly changes in interindividual distances obtained from GPS units worn by Thoroughbred dams and their foals in a pasture until weaning. The calculated inter-GPS distances were highly accurate. The regression line was linear, and the squared correlation coefficient (r²) was 0.9998. During the first month of age, the interindividual dam–dam and foal–foal distances were significantly greater than the dam–foal distance. During the second month of age, the dam–foal distance increased once and gradually decreased up to the fifth month of age. During the sixth month of age, the dam–foal distance was significantly greater than the foal–foal distance. The GPS distances calculated using Hubeny’s distance formula were useful for analyzing changes in interindividual distances in a herd of Thoroughbred dams and their foals. Most likely, calculation of the distance between GPS units worn on equine head collars is likely to become a very useful tool as an objective index for quantifying equine behavioral observations.

To establish a new system to isolate keratolytic bacteria from the hoof wall cavity (Gidoh) of a racehorse, we invented the horn powder agar-translucency (HoPAT) test and horn zymography (HZ). Using routine bacteriological techniques and these methods, we isolated five strains of keratolytic soil bacteria, which were then identified by means of 16S ribosomal RNA (rRNA) gene sequencing analysis. The findings from the study on the horse suggested that Brevibacterium luteolum played the main role in the local fragility of the hoof, eventually forming a Gidoh in coordination with four other strains of keratolytic bacteria. The double screening procedures of the HoPAT test and HZ were useful and easy techniques for isolating the keratolytic bacteria from the horn lesions.

Dystocia is often lethal for neonatal foals; however, its clinicopathological features remain largely unknown. We investigated the effect of dystocia on the foal blood profile. Venous blood samples were collected from 35 foals (5 Percheron and 30 crossbreds between Percheron, Belgian, and Breton heavy draft horses) at 0 hr, 1 hr, 12 hr and 1 day after birth. Dystocia was defined as prolonged labor >30 min with strong fetal traction with or without fetal displacement. The dystocia group (n=13) showed lower mean values for pH (P<0.01), bicarbonate (P<0.01), total carbon dioxide (P<0.05), and base excess (P<0.01) and higher mean values for anion gap (P<0.05) and lactate (P<0.01) immediately after birth than the normal group (n=22). Remarkably high pCO₂ values (>90 mmHg) were observed in three foals in the dystocia group but in none of the foals in the normal birth group immediately after birth. These results suggest that dystocia results in lactic acidosis and may be related to respiratory distress.