Gait and respiration in standardbred horses when pacing and galloping.

The research investigates how exercise intensity and mode (pacing versus galloping) affects respiratory responses, oxygen consumption, blood parameters and fatigue in standardbred horses. It discovers no significant correlation between exercise mode or intensity and PCO2 (a measure of carbon dioxide in the blood), but finds a higher PO2 (a measure of oxygen in the blood) in pacing horses at 80% maximum oxygen consumption, as well as different heart rate and fatigue markers in pacing and galloping horses.

Study Design and Methodology

• The study involved five standardbred racehorses, which were made to pace and gallop on a treadmill.
• Various parameters were gauged at specified timelines: at the start, after one and two minutes of 80% maximal oxygen consumption (VO2max) exercise, after one minute of 100% VO2max exercise, and finally after two minutes of 100% VO2max in galloping horses.
• The exercise continued until the horses registered signs of fatigue.
• Arterial blood was collected at different points, for analysis of oxygen and carbon dioxide tensions, haemoglobin saturation, and pH levels.
• Venous blood temperature was also recorded.

Key Findings

• The study found that pacing horses showed signs of fatigue more rapidly than the galloping ones—averaging around 7.2 minutes compared to 8.0 minutes in galloping horses.
• Interestingly, the level of PCO2 remained within a certain range—41.1 to 66.8 torr—irrespective of the gait or intensity of exercise and even during periods of hyperthermia and acidosis.
• However, a higher PO2 was observed in pacing horses when exercising at 80% VO2max compared to the galloping ones.
• The arterial blood pH showed a decrease from 7.428 during pacing at 5m/sec-1 to 7.250 when the horses reached the point of fatigue.

Conclusion

• The study concludes that the type of gaits (pacing or galloping) and the intensity of exercises do not significantly affect the level of PCO2. However, pacing horses demonstrated a higher PO2 at 80% VO2max and showed signs of fatigue faster than galloping horses.
• The result can provide further insights into the physiological response of horses to different types of exercise which can be valuable in training and medical intervention strategies in equine sports.