Plasma constituents during incremental treadmill exercise in intact and splenectomised horses.

The research article tested the blood of intact and splenectomised horses after incremental exercise on a treadmill and found significant changes in plasma osmolality, plasma protein concentration, and plasma potassium concentration. There was no significant change in plasma sodium concentration.

Subjects and Testing Method

• The test subjects were six intact horses and six mares that had been splenectomised, meaning their spleens had been removed.
• Each horse was subjected to an incremental exercise test on a treadmill. This test involved progressively increasing the treadmill speed till it reached 7 m/sec.
• Blood samples were taken at rest and after each minute-step of the test with the goal of studying the fluid and electrolyte changes associated with exercise and how the spleen influences these changes.

Results and Findings

• Through the testing, it was found that exercising at a speed of 7 m/sec resulted in significant increases in plasma osmolality, which refers to the measure of the concentration of solutes in the blood. The increase was 9.9% in intact horses and 6.2% in splenectomised horses.
• Plasma protein concentration significantly increased by 15.8% in intact horses and 11.4% in the splenectomised horses. This implies that a decrease in plasma volume occurred due to short-term exercise.
• In addition, plasma potassium concentration saw a significant increase of 46% in intact horses and 57% in splenectomised horses suggesting that both haemoconcentration (a decrease in the fluid content of the blood) and an increase in the content of potassium in the vascular compartment were occurring.
• Meanwhile, the plasma sodium concentration did not experience significant change in either group of horses, hinting at an isotonic shift of fluid (balanced concentration) under the exercise test conditions.

Implications and Conclusions

• This research suggests a noticeable change in these blood components even during short-term exercise, even before visible signs of sweat loss become apparent. This highlights the importance of the spleen in managing fluid and electrolyte changes associated with exercise.
• The findings provide key insights into the physiological adaptations in horses during exercise and underline the role of the spleen in electrolyte and fluid balance, which could inform veterinary care strategies for equine athletes.