Assessing chronic stress in cats: measuring hair cortisol using an ELISA

Evaluating stress in shelter and institutionally owned cats is important to help guide improvements in their welfare. Welfare assessments often focus on behavior metrics and physiologic measurements, such as systemic cortisol levels. The gold standard for measuring acute stress is serum cortisol; measuring cortisol in feces and urine gives reliable time-integrated assessments of acute stress. Monitoring chronic stress requires using a matrix that accumulates cortisol over time, such as hair or nails. Hair was collected from 29 cats representing 2 populations: cats from a local shelter and cats owned by a university. Cortisol was extracted from the hair using a method established for extracting cortisol from bovine hair. We measured hair cortisol concentrations with a commercial ELISA that is marketed for human saliva. The mean cortisol concentration was 140 pg/mg for the shelter cats and 98 pg/mg for the university-owned cats. We found no significant difference in hair cortisol concentrations between the 2 groups (p = 0.793). The intra- and inter-assay CVs for the ELISA were 9.3% and 8.4%, respectively. Observed:expected ratios for spiking recovery and dilutional parallelism were 87.7 ± 25.8% and 99.7 ± 37.5%, respectively. Measurement of cortisol in hair samples may provide a noninvasive method to monitor chronic stress and acclimation in cats that live in confinement for prolonged periods.