Assessing chronic stress in sheep using wool cortisol: A comparative study of transhumant and intensive systems

Abstract

Chronic stress profoundly affects livestock welfare, productivity, and resilience, yet its dynamics across different production systems remain insufficiently understood. This study investigates chronic stress in Karayaka sheep within three distinct production systems—long-distance transhumance (LDT), short-distance transhumance (SDT), and intensive systems (IS)—using wool cortisol concentrations as a non-invasive biomarker. Wool samples were collected from 45 ewes and 30 lambs over an eight-month period (October, December, January, February, March, May, July, and September) to evaluate cortisol accumulation as a reflection of chronic stress. Cortisol levels were analyzed using ELISA immunoassay after steroid extraction. The results revealed significant impacts of production systems and sampling periods on cortisol concentrations (P < 0.05). The marginal mean of wool cortisol was higher (P < 0.05) in SDT production systems (5.49 ± 0.20 pg/mg) compared with IS (4.85 ± 0.20 pg/mg). Seasonal variations were prominent, with cortisol peaking during winter months (January–February) and declining in March (P < 0.05). Notably, cortisol concentrations decreased during high-altitude summer grazing but spiked post-migration (May). Lambs exhibited lower cortisol levels (5.11 ± 0.17 pg/mg) compared with adult sheep (5.34 ± 0.17 pg/mg). Statistical analysis underscored significant interactions between production systems, sampling periods emphasizing the interplay of environmental stressors and animal physiology. These findings highlight the linkage of stress to environmental transitions and the critical need for adaptive management strategies tailored to production systems to reduce chronic stress and improve animal productivity and to advance sustainable livestock management.