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Erythrocytes play a vital role in transporting oxygen and ensuring adequate tissue perfusion. Their structural and functional integrity is essential for optimal athletic performance in horses. Physical exercise can subject red blood cells to mechanical, osmotic and oxidative stress, which can potentially reduce membrane stability and promote haemolysis.

This study investigated the effects of moderate exercise on the resistance of erythrocytes to acid-induced haemolysis in 17 clinically healthy Holsteiner sport horses, paying particular attention to sex-specific differences. Blood samples were collected before and immediately after a standardised one-hour exercise protocol, and erythrocyte susceptibility to 0.2N HCl was assessed spectrophotometrically. Haemolysis kinetics revealed a biphasic pattern: a rapid initial lysis phase (0.5-10 minutes) was followed by slower progression to complete haemolysis (25-30 minutes).

 Exercise significantly increased erythrocyte fragility in both sexes, with stallions showing slightly higher resistance at rest. These findings suggest that physical exertion temporarily compromises the integrity of the erythrocyte membrane, primarily affecting the most vulnerable subpopulation.

The study highlights the importance of considering physiological status and sex when evaluating erythrocyte stability, and suggests that acid-induced haemolysis could be used to monitor equine athletic performance and recovery.

 

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