Veterinary medicine and science2026; 12(5); e71153; doi: 10.1002/vms3.71153

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

Turgut, F
·
Yanmaz, LE
·
Orhun, OT
·
Apaydin Yildirim, B
·
Kocaman, Y
·
Senocak, MG
·
Arslan, T
·
Aslan Canatan, V

Abstract: 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. Methods: 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. Results: 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. Conclusions: 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.

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Publication Date: 2026-08-12 PubMed ID: 42585227DOI: 10.1002/vms3.71153Google Scholar: Lookup

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Summary

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Overview

This study investigated how a standardized submaximal exercise session affects eye health indicators and oxidative stress markers in saliva and tear fluid of horses.
The aim was to understand the physiological impact of exercise on ocular parameters and the oxidative balance reflected in easily accessible body fluids.

Background

Exercise is known to act as a physiological stressor in horses, potentially increasing reactive oxygen species (ROS) that drive oxidative stress.
Oxidative stress can impact cellular health and function, making it important to monitor during physical activity.
Ocular parameters such as intraocular pressure (IOP), tear secretion (TS), and central corneal thickness (CCT) are key to maintaining eye homeostasis and health.
Saliva and tear fluid are non-invasive biological matrices that can be easily collected and may reflect systemic oxidative stress status by measuring biomarkers.

Objectives

To evaluate the effects of a 30-minute, submaximal exercise session (walk-trot-canter) on horses’ ocular parameters: IOP, TS, and CCT.
To assess changes in oxidative stress biomarkers in saliva and tear fluid pre- and post-exercise. Biomarkers studied included:
- Antioxidant enzymes: Catalase (CAT), Superoxide Dismutase (SOD), Glutathione (GSH)
- Markers of oxidative damage: Malondialdehyde (MDA)
- Ischemia-modified albumin (IMA), indicating oxidative stress-related tissue ischemia

Methods

Thirty-six clinically healthy Arabian horses participated.
The exercise involved 30 minutes of standardized submaximal work: progressing through walking, trotting, and cantering.
Measurements were taken immediately before and after exercise:
- Heart rate (to confirm physiological stress response)
- Ocular parameters:
  - Schirmer tear test-1 (to assess tear secretion)
  - Rebound tonometry (to measure intraocular pressure)
  - Ultrasonic pachymetry (to determine central corneal thickness)
- Collection of saliva and tear fluid samples for biochemical analysis of oxidative stress biomarkers.
Statistical analysis included:
- Shapiro-Wilk test to assess data normality.
- Paired-samples t-tests or Wilcoxon signed-rank tests to compare pre- and post-exercise values.

Results

Heart rate significantly increased post-exercise, confirming the exercise was physiologically demanding (p < 0.001).
Ocular parameters:
- Intraocular pressure (IOP) showed no significant change.
- Central corneal thickness (CCT) remained stable.
- Tear secretion (TS) modestly decreased (p = 0.033), indicating a mild effect on tear production.
Oxidative stress biomarkers in saliva:
- CAT and SOD enzyme activities increased significantly (p < 0.001), reflecting an upregulation of antioxidant defenses.
- MDA levels decreased significantly (p < 0.001), suggesting reduced lipid peroxidation or oxidative damage after exercise.
- GSH and IMA showed no significant changes.
Oxidative stress biomarkers in tear fluid:
- CAT, GSH, and SOD all increased significantly, indicating antioxidant activity enhancement.
- IMA and MDA levels decreased significantly, mirroring findings in saliva for indicators of oxidative damage.

Conclusions and Implications

The 30-minute submaximal exercise induced a shift towards increased antioxidant activity in both saliva and tear fluid of horses.
This antioxidant-dominant response suggests that exercise stimulates protective biochemical adaptations against oxidative stress in these horses.
Ocular health parameters remained largely unaffected except for a mild decrease in tear secretion, which may reflect transient physiological changes without significant ocular stress.
Tear fluid, alongside saliva, can serve as a valuable, non-invasive tool for monitoring oxidative balance and physiological responses to exercise in horses under routine training conditions.
These findings support the importance of antioxidant defenses during exercise and highlight the potential utility of tear fluid biomarkers in veterinary sports medicine and equine health monitoring.

Cite This Article

APA

Turgut F, Yanmaz LE, Orhun OT, Apaydin Yildirim B, Kocaman Y, Senocak MG, Arslan T, Aslan Canatan V. (2026). Effects of Exercise on Ocular Parameters and Oxidative Stress Biomarkers in Saliva and Tear Fluid of Horses. Vet Med Sci, 12(5), e71153. https://doi.org/10.1002/vms3.71153

Publication

Veterinary medicine and science

ISSN: 2053-1095

NlmUniqueID: 101678837

Country: England

Language: English

Volume: 12

Issue: 5

Pages: e71153

Researcher Affiliations

Turgut, Ferda

Department of Surgery, Faculty of Veterinary Medicine, Cukurova University, Adana, Turkey.

Yanmaz, Latif Emrah

Department of Surgery, Faculty of Veterinary Medicine, Burdur Mehmet Akif Ersoy University, Burdur, Turkey.

Orhun, Omer Tarik

Department of Surgery, Faculty of Veterinary Medicine, Necmettin Erbakan University, Konya, Turkey.

Apaydin Yildirim, Betul

Department of Biochemistry, Faculty of Veterinary Medicine, Ataturk University, Erzurum, Turkey.

Kocaman, Yakup

Department of Surgery, Faculty of Veterinary Medicine, Yozgat Bozok University, Yozgat, Turkey.

Senocak, Mumin Gokhan

Department of Surgery, Faculty of Veterinary Medicine, Ataturk University, Erzurum, Turkey.

Arslan, Taner

Department of Surgery, Faculty of Veterinary Medicine, Ataturk University, Erzurum, Turkey.

Aslan Canatan, Vildan

Department of Surgery, Faculty of Veterinary Medicine, Cukurova University, Adana, Turkey.

MeSH Terms

Animals
Horses / physiology
Oxidative Stress / physiology
Tears / chemistry
Physical Conditioning, Animal / physiology
Biomarkers / metabolism
Saliva / chemistry
Male
Female
Intraocular Pressure / physiology

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