Restoration of water and electrolyte balance in horses after repeated exercise in hot and humid conditions.

The research study investigated the impact of administering an isotonic glucose-electrolyte solution to horses after repeated exercise in hot and humid conditions. The study found that this method of rehydration was more effective than water in ensuring the horses’ recovery and acclimation to the conditions.

Study Design

In the study, nine adult riding horses were required to perform a competition exercise test (CET) and then a standardised exercise test (SET) after 24 hours. These tests were conducted five times at two-week intervals. The ambient conditions for the tests were approximately 28 degrees Celsius and 58% humidity.

After each CET, except for the last trial, the horses were given an isotonic glucose-electrolyte solution via a nasogastric tube. After the last trial, they were given just water.

A range of measurements were taken in this study, including:

• Blood lactate
• Plasma concentration of aldosterone, arginine vasopressin, protein, sodium, potassium, chloride, magnesium and calcium
• Heart rate
• Plasma volume (PV)
• Red cell volume

Findings of the Study

The study found that mean weight loss after each CET was 3.1%, with no significant change observed throughout the study. The post-exercise body weight loss (BWL2) decreased over time. After the final trial, where only water was given, the weight loss increased to -2.5%.

Interestingly, heart rate correlated significantly with BWL2 where BWL2 was greater than -1.2%.

Conclusion

The results from this study indicate that horses are better able to acclimate to exercise in hot and humid conditions when given an isotonic glucose-electrolyte solution post-exercise, as it assists in better recovery. This recovery and acclimation were evident in the increased plasma volume, lower peak lactate concentrations and heart rate, and a lesser decrease in concentrations of sodium and chloride in the horses’ blood.

It was concluded that changes in body weight provide good indicators of a horse’s recovery after exercise in such conditions, and that administering an isotonic glucose-electrolyte rehydration solution post-exercise appears to be more beneficial in overcoming dehydration than giving water alone.