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The aim of this study was to evaluate the effects of intraspecific social exposure (socialization vs rest) and habituation factors on the levels of urinary serotonin and cortisol [corrected respectively for creatinine to give the serotonin-creatinine ratio (5-HT/Cr) and cortisol-creatinine ratio (C/Cr)] and how they fluctuate in dogs. The frequency of marking during social sessions was recorded to evaluate its relationship with physiological parameters. The effects of covariates on 5-HT/Cr and C/Cr were assessed using a linear mixed models. 5-HT/Cr values were higher at dawn than at dusk during resting days, however, this difference is less evident after socialization sessions. During rest days, there was a trend for a decrease in C/Cr between dawn and dusk, while during social exposure days there was an opposite trend. Significant interactions were found between social exposure vs rest (P = 0.0005) and social exposure vs sessions (P = 0.002). Urine marking was more frequent in male than female dogs. The frequency of urine marking also appeared to be positively associated with C/Cr. Non-invasive monitoring of physiological markers could be a useful tool in assessing behaviour modulation following intraspecific socialization exposure. C/Cr was characterized by high individual variability and interactions with examined factors. The identification of new markers such as serotonin for assessing welfare in dogs is highly desirable., (Copyright © 2019 Elsevier Inc. All rights reserved.)

To evaluate parallel circadian rhythms in salivary and serum cortisol concentrations during 48-h period, sampling was performed in six clinically healthy dogs of various breeds housed under natural photoperiod in spring (sunrise 05:20, sunset 20:20). Saliva and blood samples were taken every 3 h for a 48-h period to determine the daily changes in salivary and serum cortisol concentrations. The relationship between salivary and serum cortisol level was determined as well. In the two-day period of monitoring, salivary and serum cortisol concentrations showed the same trend. Their levels started to increase at sunrise and reached their peak in the middle of the photophase. Both parameters showed a high robustness of rhythm. A positive correlation between salivary and serum cortisol concentration was observed during the day 1 and 2. Acrophase and robustness of rhythm showed no statistically significant difference between salivary and serum cortisol concentrations. We can claim that salivary cortisol, a measure of free cortisol, follows the circadian rhythm of serum cortisol. Therefore, saliva sampling is a valid and non-invasive technique useful in chronomedicine to estimate free cortisol. [ABSTRACT FROM AUTHOR]