Salivary cortisol concentrations and behavior in a population of healthy dogs hospitalized for elective procedures

Abstract

Identification of severe stress in hospitalized veterinary patients may improve treatment outcomes and welfare. To assess stress levels, in Study 1, we collected salivary cortisol samples and behavioral parameters in 28 healthy dogs hospitalized prior to elective procedures. Dogs were categorized into two groups; low cortisol (LC) and high cortisol (HC), based on the distribution of cortisol concentrations (< or ≥0.6μg/dL). We constructed a stress research tool (SRT) based on three behaviors (head resting, panting and lip licking) that were most strongly related to salivary cortisol concentrations. In Study 2, we collected salivary cortisol samples from 39 additional dogs, evaluated behavior/cortisol relationships, assigned each dog to an LC or HC group, and tested the ability of the SRT to predict salivary cortisol. Median (interquartile range) salivary cortisol concentrations were not different between Study 1 (0.43μg/dL, 0.33–1.00μg/dL) and Study 2 dogs (0.41μg/dL, 0.28–0.52μg/dL). The median salivary cortisol concentration was significantly lower (P≤0.001) in LC versus HC dogs in each study; (Study 1 LC: 0.38μg/dL (0.19–0.44), n=19, HC: 2.0μg/dL (1.0–2.8), n=9, and Study 2 LC: 0.35μg/dL (0.25–0.48), n=28, HC: 0.89μg/dL (0.66–1.4), n=7). In Study 1, three behaviors were found to be associated with salivary cortisol concentrations. Duration of head resting was negatively associated with salivary cortisol (ρ=−0.60, P=0.001), panting and lip licking were positively associated with cortisol (ρ=0.39, P=0.04, and 0.30, P=0.05, respectively), head resting (P=0.001) and panting (P=0.003) were also associated with LC/HC group assignment. In Study 2 dogs, the three behaviors correlated (but not significantly) with salivary cortisol concentration; of the three, only head resting was significantly associated with LC/HC group assignment (P=0.03). The SRT derived from Study 1 was effective at prediction of salivary cortisol concentrations when applied to 20min but not 2min of behavioral data from Study 2. Additionally, we note that dexmedetomidine and butorphanol sedation more than 6h prior to measurement was found to be significantly (P=0.05) associated with lower salivary cortisol concentrations when compared to unsedated dogs. Our work offers support for eventual construction of a rating tool that utilizes the presence or absence of specific behaviors to identify higher salivary cortisol concentrations in dogs subjected to hospitalization, which may be tied to greater psychogenic stress levels. Future work to investigate the effects of stress on dogs and its mitigation in clinical situations may be approached by studying a combination of parameters, and should consider the possible beneficial effects of sedatives.