Blood and muscle metabolic responses to draught work of varying intensity and duration in horses.

This study examines the metabolic responses in horses’ blood and muscle during various intensities and durations of treadmill exercise. It found that oxidative metabolism is crucial for energy supply during low speed exercise, while glycogenolysis and phosphagen breakdown become significant when speed increases.

Research Methodology

• Three standardbred trotters (a breed of horse) were involved in this study.
• The horses performed treadmill exercises under three different conditions – a speed of 2 m/s with a draught load of 34 kiloponds (kp) (test 1), a speed of 2 m/s with 80 kp (test 2), and a speed of 7 m/s with 34 kp (test 3). A draught load refers to the resistance the horse encounters during exercise, mimicking pulling a weight or carriage.

Observations

• Heart rate: The average heart rates of the horses increased with the intensity of the exercise – they were 111 beats per minute (bpm) during test 1, 157 bpm during test 2, and 197 bpm during test 3.
• Plasma free fatty acids: The plasma free fatty acids, which are produced when the body burns fat for energy, only showed an increase during tests 1 and 2.
• Impact on blood lactate and muscle glucose: Blood lactate, muscle glucose-6-phosphate, and muscle lactate concentrations were found to be low during tests 1 and 2 but high after test 3, indicating that more glycolysis occurred with an increase in exercise intensity. This also resulted in significantly higher muscle glycogen utilisation in test 3.
• Muscle creatine phosphate and adenosine triphosphate concentrations, which play important roles in energy metabolism in muscle, decreased after test 3, implying that higher intensity exercise depletes these energy stores.

Conclusion

• The results indicate that oxidative metabolism plays an essential role in supplying energy to the horses’ muscles during exercises performed at a lower velocity, irrespective of the draught load (both 34 and 80 kp).
• When the exercise intensity increases with a draught load of 34 kp, other metabolic pathways like glycogenolysis and phosphagen breakdown become more important for providing the necessary energy.