NON-INVASIVE MEASUREMENT OF OXIDATIVE STRESS IN SENIOR AND EXERCISING HORSES
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Abstract
The published data regarding oxidative stress in horses is generally concerned with blood and muscle samples. The aim of this thesis was to use non-invasive markers as a novel approach to investigate cellular stress in performance and senior horses. In addition, urine was analysed using IH NMR spectroscopy and renal insult during ageing and exercise was investigated using urinary N-acetyl-beta-D-glucosaminidase (NAG) activity.
The results demonstrated that urinary thiobarbituric acid reactive substances (TBARS) in horses could be measured using a method adapted from Vagi (1976) and were significantly decreased following supplementation with antioxidants in the form of dandelion and milk thistle (p<O.05). Urinary TBARS were seen to decrease in horses supplemented with vitamin E at a level of 4mglkg bodyweight, but subsequently were unaffected in horses performing a sub-maximal exercise test on a treadmill when supplemented with vitamin E at a level of 3 mg/kg bodyweight.
Urinary TBARS were seen to increase with age (P<O.05), consistent with increased lipid peroxidation in senior horses. Analysis using 1 H NMR spectroscopy revealed higher levels of aromatic amino acids in the urine of senior horses (p<O.05) and proteinuria quantification using the biuret assay demonstrated increased total proteinuria in the urine of senior horses compared to young horses (p<O.05). This indicated that subtle changes in renal, hepatic and endocrine functions may be evident in senior horses.
TBARS in equine sweat could be measured using a method adapted from Vagi (1976) and were significantly decreased in horses performing a sub-maximal exercise test on a treadmill, following vitamin E supplementation (p<O.05). In addition, free radical scavenging activity of equine saliva could be measured using a method adapted from Atsumi et al (1999). Urinary NAG activity proved to be difficult to measure in the horse and may require further investigation to establish its potential use as a marker of renal insult in horses.