Oxidative stress markers in different age ranges of healthy horses.

Oxidative stress results from an imbalance between oxidants and antioxidants, impairing cellular functions and contributing to diseases and aging. Despite the growing interest in oxidative stress, studies specifically evaluating the influence of age on laboratory and oxidative stress parameters in clinically healthy horses remain limited. Thus, this study aimed to evaluate the influence of age on laboratory and oxidative stress parameters in clinically healthy horses. A total of 152 clinically healthy horses (80 females and 72 males) were selected, including young horses aged 3 to 48 months (n = 50), adult horses aged 96 to 168 months (n = 76), and elderly horses aged 240 to 360 months (n = 26). Complete blood count, biochemical profile and assessment of oxidative stress were conducted using specific methodologies: total antioxidant capacity (TAC), total oxidant capacity (TOC), and the antioxidants uric acid and albumin. TAC was determined by the inhibition of ABTS cation reduction alone (TAC-ABTS), or in the presence of peroxidase (TAC-ABTS+HRP), ferric reducing antioxidant power (TAC-FRAP), and cupric reducing antioxidant capacity (TAC-CUPRAC). Data were analyzed using ANOVA or the Kruskal-Wallis test, and differences were considered significant when P < 0.05. Young horses showed higher values for red blood cells (RBC), white blood cells (WBC), lymphocytes, monocytes, and platelets than adult and aged horses, as well as higher uric acid and TAC-CUPRAC values than aged horses. In contrast, young horses exhibited lower mean corpuscular volume (MCV) and TAC-ABTS+HRP values than adult and aged horses. Adult horses, in turn, exhibited lower AST values and creatinine values, accompanied by higher red blood cell distribution width (RDW), compared with young horses. Age-related alterations in laboratory parameters, particularly oxidative stress biomarkers, were observed in clinically healthy horses. Collectively, these findings suggest that age should be considered when interpreting these parameters and emphasize the importance of evaluating multiple biomarkers for a more comprehensive characterization of redox status.