Effects of Exercise on Ocular Parameters and Oxidative Stress Biomarkers in Saliva and Tear Fluid of Horses.

BACKGROUND

Physical exercise is a physiological stressor in horses and may induce oxidative stress through increased production of reactive oxygen species. Saliva and tear fluid are accessible non-invasive matrices that may reflect oxidative balance, while ocular parameters including intraocular pressure (IOP), tear secretion (TS) and central corneal thickness (CCT) are key components of ocular homeostasis.

OBJECTIVE

To evaluate the effects of a standardised submaximal exercise session on IOP, TS and CCT, and on oxidative stress biomarkers (CAT, SOD, GSH, MDA, IMA) measured in saliva and tear fluid.

METHOD: Thirty-six clinically healthy Arabian horses underwent a 30-min submaximal field exercise (walk-trot-canter). Heart rate, ocular parameters (Schirmer tear test-1, rebound tonometry, ultrasonic pachymetry) and saliva and tear fluid samples were collected immediately before and after exercise. Data normality was assessed using the Shapiro-Wilk test, and paired-samples t-tests or Wilcoxon signed-rank tests were applied as appropriate.

RESULT: Heart rate increased significantly after exercise (p < 0.001). IOP and CCT did not change significantly, whereas TS decreased modestly (p = 0.033). In saliva, CAT and SOD increased and MDA decreased (all p < 0.001), with no changes in GSH or IMA. In tear fluid, CAT, GSH and SOD increased, while IMA and MDA decreased significantly.

CONCLUSION

Submaximal exercise elicited antioxidant-dominant shifts in both saliva and tear fluid, while ocular parameters remained largely stable except for a mild reduction in TS. Tear fluid, alongside saliva, may provide complementary information on exercise-associated physiological and oxidative responses in horses under routine training conditions.