Activities of selected aerobic and anaerobic enzymes in the gluteus medius muscle of endurance horses with different performance records.

The study investigated the activity levels of certain aerobic and anaerobic enzymes in the gluteus medius muscle of endurance horses. The results showed that horses with better performance records had higher aerobic enzyme activity and relatively lower anaerobic enzyme activity.

Sampling and Division of Horses

• Researchers took muscle samples from 36 different endurance horses, each around 8.42 +/- 2.85 years old and of both sexes.
• These horses were categorized based on their athletic performance in endurance events over the past two to three years. Twenty were identified as ‘excellent performers’ due to having greater average speed in their three fastest records, while the remaining 16 were classified as ‘moderate performers’.

Enzyme Analysis and Findings

• The researchers examined these muscle samples for the activities of three specific enzymes: citrate synthase (CS), 3-OH-acyl-CoA-dehydrogenase (HAD), and lactate dehydrogenase (LDH).
• CS is used as an indicator of citric acid cycle activity, which is a key process in aerobic metabolism.
• HAD signifies lipid oxidation, another process involved in aerobic metabolism, and LDH represents anaerobic metabolism processes.
• The 20 horses classified as excellent performers displayed higher activity levels of CS (p-value < 0.001) and HAD (p-value < 0.02) compared to the 16 classified as moderate performers. This means that their muscles exhibited stronger aerobic metabolic activity.
• The deeper the muscle samples were taken from, the higher the percentage increase in activity of CS (up by 65%) and HAD (up by 75%). Meanwhile, the activity of LDH, the enzyme representing anaerobic metabolism, decreased by 23%.

Correlations and Interpretation

• There was a strong linear correlation between the activity ratios of LDH/CS and LDH/HAD and the muscle sample’s depth in both excellent and moderate performance groups (p-value < 0.001).
• The regression lines’ intercepts were higher for the moderate performers versus the excellent performers (p-value < 0.001 and p-value < 0.01 for the two ratios respectively). This implies that the horses with better performance records show greater aerobic capacity (as indicated by the CS and HAD activity) and relatively lower anaerobic capacity (as indicated by the LDH activity) in the gluteus medius muscle.
• Thus, the study indicates a possible relationship between improved endurance performance in horses and higher activity levels of aerobic enzymes compared to anaerobic ones in their muscle tissues.