Evaluation of some oxidative stress markers in ovis aries during different experimental conditions

Background: Oxidative stress (OS) results from an imbalance between the production of reactive oxygen species (ROS) and antioxidant defense mechanisms, playing a critical role in the pathogenesis of metabolic diseases in veterinary medicine. Objectives: This study aimed to evaluate oxidative stress markers—specifically dROMs (reactive oxygen metabolites), Oxy-adsorbent capacity, and SHp (sulfhydryl groups)—in Comisana ewes under various physiological and management conditions, including shearing, road transportation, different reproductive stages, and circadian rhythms. Methods: Ten clinically healthy, 3-year-old ewes were monitored. Blood samples were collected to assess markers during shearing (pre-, post-, and 1–5 days post-shearing), road transport (490 km; pre-, post-, and 8–48h post-transport), and reproductive cycles (days 1, 40, and 200 of lactation, and dry period). Circadian rhythms were evaluated by sampling every 3 hours over a 24-hour period. Data were analyzed using ANOVA and a trigonometric statistical model (single cosinor procedure). Results: Results demonstrated that shearing and road transportation induce a significant increase in dROMs, accompanied by a compensatory rise in Oxy-adsorbent and SHp levels, indicating a disruption of homeostatic balance. During lactation, a significant increase in oxidative markers was observed compared to the early stages of lactation, suggesting that high metabolic requirements are directly proportional to ROS formation. Furthermore, a significant circadian rhythm was identified for all markers, with a nocturnal acrophase (approx. 21:00–21:30) and high rhythm robustness. Conclusions: The findings confirm the existence of a synergism between oxidative stress and circadian rhythms in ewes. Proper zootechnical management and targeted nutritional strategies are essential to mitigate oxidative stress and ensure animal welfare and productivity.