Haematological and respiratory gas changes in horses and mules exercised at altitude (3800 m).

This research study observed the physiological reactions of horses and mules when subjected to exercise at high altitudes, specifically focusing on changes to their haematological and respiratory functioning. The study found that horses and mules exhibit different adaptive responses at high altitudes, with horses showing higher levels of packed cell volume (PCV) and 2,3-diphosphoglycerate (2,3-DPG), both of which are important aspects of oxygen transport in the blood.

Study Design and Methodology

• The study involved six horses and five mules, with baseline tests conducted at a low altitude of 225 meters. Post-exercise tests were conducted immediately after a prescribed exercise routine.
• The exercise routine consisted of trotting up a 6% incline for two kilometers.
• The animals were then transported to a high altitude of 3800 meters for 13 days, during which period the blood samples were taken at rest and post-exercise, following the same prescribed exercise routine.
• The haematological and respiratory gases were analyzed using repeated measures analysis of variance (ANOVA) to identify any significant changes.

Results

• At the low altitude, both horses and mules demonstrated similar heart rates, both at rest and post-exercise.
• However, mules were found to have an 8% lower resting PCV than horses, and a 20% lower PCV during exercise.
• Horses showed significantly higher levels of 2,3-DPG, a compound that facilitates oxygen release from hemoglobin, at rest and post-exercise.
• Upon exposure to high altitude exercise, both horses and mules showed increased PCV. However, this increase was more significant in horses than mules.
• Exercise at high altitude also led to an increase in 2,3-DPG in both groups, but the increase was attenuated in mules.
• Both groups at high altitude were alkalotic compared to low altitude, suggesting the bodies were compensating for lower oxygen levels at high elevation by reducing the acidity of the blood. No significant difference was identified between the two groups in this regard.

Conclusions

• The primary differences between horses and mules, based on this study, were noted in PCV and 2,3-DPG levels, which were higher in horses at both low and high altitudes.
• While mules’ attenuated response in PCV might indicate better adaptation to high altitude, lower levels of 2,3-DPG might suggest otherwise due to its critical role in oxygen delivery to tissues.
• However, no significant differences were identified between horses and mules regarding other variables during the exercise bout.