Nail cortisol for welfare assessment in shelter and owned cats

Shelter cats are vulnerable to stress due to the challenging circumstances they face, including confinement, unfamiliar environments, people, and animals. This vulnerability often leads to welfare issues, emphasizing the importance of assessing and improving their well-being. Measuring cortisol levels, a stress hormone, from nails has emerged as a non-invasive method to evaluate the stress response in humans and other animals. This study aimed to apply nail cortisol for welfare assessment in cats by measuring and comparing nail cortisol concentrations (NCCs) of owned cats and shelter cats living in different conditions. Nails of 31 owned cats (OC), 29 shelter cats living in favorable conditions (FS), and 27 shelter cats living in unfavorable conditions (US) in Thailand and Vietnam were collected twice with an interval of approximately 28 days, and the information about their living conditions was recorded at the 2nd trim for analysis. Nail clippings were washed, ground, and extracted with methanol. The cortisol extract was dried, reconstituted, and measured using the ELISA technique. Associations between NCCs and environmental factors were also examined to assess their possible influences on the welfare of cats. For both trims, the NCCs of the US group were significantly higher than those of the FS and OC groups. There was no significant difference in NCC between males and females. NCCs positively correlated with animal density and dog exposure, while negatively correlated with the number of litterboxes, captivity with more free roaming time, air-conditioning environment, the number of enrichment types, the presence of hiding places, elevated areas, places for looking outside, scratching structures, and toys. A significant negative correlation was also found between the 2nd-trim NCCs and time living in the shelter of FS cats, but not US ones. These data suggested that providing better living conditions can positively impact welfare, as assessed by NCCs. To conclude, nail cortisol can be used to non-invasively assess the welfare of cats, especially under the influence of long-term factors. Suboptimal living conditions may cause chronic stress and affect their well-being. The proposed method can be used to measure nail cortisol concentrations of cats living in different conditions.