Non-invasive Assessment of Social Isolation Induced Stress in Tharparkar Calves ( <i>Bos indicus</i> )

Accurate and welfare-friendly methods for stress detection in livestock are essential for advancing animal husbandry practices. This study investigated the efficacy of fecal cortisol metabolites (FCM) as a non-invasive biomarker for assessing stress induced by social isolation in calves. Sixteen Tharparkar calves were subjected to an 8-day experimental period, which was divided into three distinct phases: pre-isolation (3 days), isolation (2 days) and reunion (3 days). The experimental design consisted of four replications, each with four calves. Behavioral and physiological observations were concurrently recorded to validate FCM levels. During the isolation phase, significant behavioral deviations were observed, including reduced lying time and feeding, along with increased standing, walking and idling (p < 0.05). Heart and respiration rates also increased significantly (p < 0.05), while rectal temperature remained unchanged. However, fecal cortisol metabolite concentrations increased significantly during isolation (p < 0.001), mirroring serum cortisol trends and remained elevated even after reunion. These findings confirmed that FCM provided a robust, stress-sensitive and non-invasive alternative to serum-based hormonal assays. Therefore, FCM can be used as a potential tool for fecal cortisol monitoring and as a practical tool for welfare assessment in bovine.