Changes in equine metabolic characteristics due to exercise fatigue

Area of Science:

• Equine Exercise Physiology
• Biochemistry

Background:

• Understanding physiological responses to exercise is crucial for equine athletes.
• Metabolic and acid-base balance are key indicators of exercise intensity and fatigue.

Purpose of the Study:

• To characterize changes in blood pH, lactate, free fatty acid, bicarbonate, and ammonia concentrations.
• To assess muscle glycogen depletion following strenuous exercise to fatigue in horses.

Main Methods:

• Eight horses performed an exercise test on a motorized treadmill at 4.5 m/s and a 9% grade until fatigue.
• Blood samples were analyzed for pH, lactate, free fatty acid, bicarbonate, and ammonia.
• Muscle biopsies (gluteus medius) were analyzed for glycogen concentration.

Main Results:

• Significant changes (P < 0.05) were observed in all measured variables at fatigue compared to baseline.
• Plasma lactate increased from 7.8 to 94.3 mg/dl, and ammonia increased from 66.7 to 136.9 µmol/L.
• Blood pH decreased from 7.37 to 7.28, bicarbonate decreased from 31.3 to 21.1 mM, and muscle glycogen decreased by 25%.

Conclusions:

• Strenuous exercise to fatigue in horses induces significant metabolic acidosis and substrate depletion.
• These findings provide insights into the physiological limitations and biochemical adaptations during high-intensity equine exercise.