Relationship between markers of blood oxidant status and physiological variables in healthy and heaves-affected horses after exercise.

This study explored the connection between physiological responses to exercise and blood oxidant markers in both healthy horses and those suffering from heaves, a common equine respiratory disease. The research found some correlations in the healthy horses but suggests the blood oxidant status in heaves-affected horses may rely more on their respiratory condition than exercise.

Research Methodology

• The study involved a total of 22 horses; 7 healthy animals, 8 suffering from heaves but in remission, and 7 experiencing a heaves crisis. All subjects underwent a standardised exercise test (SET) with gradually increasing intensity.
• During the exercise, the researchers monitored various physiological factors such as heart rate (HR), packed cell volume (PCV), venous plasma lactate (LA), and arterial oxygen tension (PaO2).
• The team also analysed the blood samples taken at rest, at peak exercise intensity, and 15 and 60 minutes after the exercise to assess oxidant markers such as uric acid (UA), 8-iso-PGF2alpha, and reduced (GSH) and oxidised glutathione (GSSG).

Findings

• Heaves significantly impacted the oxidant markers in the horses, leading the team to carry out correlation analyses between physiological variables and oxidant markers for each horse group separately.
• In healthy horses, there was a positive correlation between uric acid (UA) analysed at peak exercise intensity and lactate (LA). Additionally, reduced glutathione (GSH) analysed at peak exercise and 15 minutes post-exercise correlated positively with arterial oxygen tension (PaO2).
• In both healthy horses and heaves-suffering horses in remission, GSH and oxidised glutathione (GSSG) at peak exercise were negatively correlated with heart rate (HR).
• However, the team found no significant correlation between 8-iso-PGF2alpha – a marker of lipid peroxidation – and physiological variables.

Conclusion

• While certain correlations could be drawn between physiological reactions to exercise and oxidant markers in healthy horses, it seemed that in heaves-affected horses, their blood oxidant status was more related to their respiratory disease than exercise.
• The researchers suggest conducting further studies to see if antioxidant supplementation could positively influence the oxidant-antioxidant balance in exercising horses.