Electrolyte and total protein changes in nonheat acclimated horses performing treadmill exercise in cool (20 degrees C/40%RH), hot, dry (30 degrees C/40%RH) or hot, humid (30 degrees C/80%RH) conditions.

The research investigates the changes in electrolyte and total protein levels in non-heat acclimatized horses executing treadmill exercises under varying environmental conditions: cool dry (20°C/40% Relative Humidity), hot dry (30°C/40% RH), and hot humid (30°C/80% RH). The study noted the significant influence of exercise and environmental conditions on electrolyte and total protein levels, offering insights into the physiological impact of humidity and temperatures on exercising horses.

Research Methodology

• Four horses underwent a simulated competition exercise test (CET) that replicated the physiological and metabolic stresses of a 3-day-event’s Speed and Endurance test. This test was run under three different climate conditions: cool dry, hot dry, and hot humid.
• Venous blood samples were collected at predetermined intervals throughout the CET and the initial 30-min recovery period. Further blood samples were taken at 2-hour and 24-hour intervals after completing the final 8-minute canter.
• The research examined the influences of exercise, environmental condition, and the individual horse on venous blood levels of total protein (TP) and various electrolytes—sodium, potassium, chloride, calcium, magnesium, and phosphate.

Findings and Observations

• All horses managed to complete the CET under cool dry and hot dry conditions. However, only one horse managed to finish the exercise under hot humid conditions.
• Exercise significantly impacted all the examined parameters, which correlates with observations reported in previous field competitions.
• Both time and individual horse significantly influenced TP, sodium, and chloride levels.
• The environmental conditions significantly affected all parameters. However, apart from chloride and TP levels, these variations were not deemed physiologically substantial.
• A meaningful interaction between time and environmental condition was seen in chloride and TP only. Mean chloride values were higher in the first cool dry session than the second one or in the hot and humid, or hot and dry conditions.
• The total protein concentration was higher under hot humid conditions after 2 minutes into Phase D exercise and during the initial recovery period, returning to pre-exercise values less swiftly.
• While individual variations were found in estimated cation losses, no consistent influence of environmental condition was observed.
• Despite similar estimated fluid losses post-exercise in hot dry and hot humid conditions, bodyweight restoration was slower following hot humid sessions.

Conclusion

In summary, the research found that changes in electrolytes and total protein levels in horses performing treadmill exercises were significantly influenced by exercise and environmental conditions. While the environmental conditions did significantly impact all parameters, these variations were not generally deemed physiologically relevant, barring chloride and total protein levels.