Differences in the ventilatory responses of horses and ponies to exercise of varying intensities.

This study investigates the differences in breathing responses between horses and ponies when they perform exercise of varying intensities. The findings suggest that, unlike ponies, horses experience low levels of oxygen and high levels of carbon dioxide in their blood when exercising at high intensity, indicating that their respiratory system struggles to meet the increased metabolic demand.

Research Methodology

• The study involved six Thoroughbred horses and five ponies. Horses’ average weight was approximately 501 kg, and ponies’ average weight was significantly less at approximately 164 kg.
• Each animal was made to exercise on a 10% slope for 2 minutes at speeds that required 60% of their maximum oxygen consumption and for at least 1 minute at speeds that required 115% of their maximum oxygen consumption.
• Various parameters were measured just before exercise and during the last 15 seconds of exercise at each intensity. These parameters included oxygen consumption (VO2), as well as blood levels of oxygen (PaO2) and carbon dioxide (PaCO2).
• Other measurements related to ventilatory system functionality were also collected. These included measurements of acid-base balance, tidal volume, minute ventilation, peak inspiratory and expiratory flow, and maximal changes in transpulmonary pressures.

Key Findings

• Findings confirmed that ponies do not show low oxygen (hypoxaemia) or high carbon dioxide (hypercapnoeic) levels in their blood during exercise, unlike horses.
• Horses were found to be less capable of producing an appropriate breathing response to exercise, even though they demonstrated higher measurements for several ventilatory parameters. Specifically, horses had higher values for maximal changes in transpulmonary pressures, peak inspiratory and expiratory flow, and minute ventilation, when normalized by their respective body weights to the power of 0.75 (kg^0.75).
• Horses showed lower environment-specific and metabolic weight-based ventilation values at similar absolute workloads. Their blood carbon dioxide levels and bicarbonate ions were higher, and their ventilatory equivalent for oxygen (the volume of gas ventilated per unit of oxygen consumed) was lower. These results imply that horses’ metabolic demand surpasses their ventilatory system’s capacity when performing high-intensity exercise.
• In contrast, due to their lower athletic capacities, ponies can match their ventilatory responses to their metabolic requirements during exercise.

Conclusions

• The study offers a clear insight into the physiological differences between horses and ponies during exercise, highlighting how species and size can impact respiratory and metabolic responses to physical exertion.
• Understanding these constraints can influence training methods for horses, to prevent respiratory and metabolic imbalances and ensuing health issues during high-intensity activities.