Assessment of Physiological Stress to Environmental Challenges by Measurement of Salivary Cortisol in Dogs

Abstract

16 shelter dogs = S group) were included in the study. The dogs were divided into two groups according to the results of the behavior test (H group = dogs with high sociability

L group = dogs with low sociability). In the H group, the salivary cortisol concentration at P1 was 0.3848 ± 0.0969 μg/dl and at P2 was 0.3577 ± 0.0981 μg/dl. In the L group, the concentration at P1 was 0.5593 ± 0.0755 μg/dl, and the concentration at P2 was 0.6527 ± 0.0781 μg/dl. The ratio of the concentration at P2 to that at P1 (P2/P1) were significantly different between the groups (p=0.008). Likewise, the differences in the concentration between P1 and P2 (P2 − P1) were −0.0272 ± 0.03 μg/dl in the H group and 0.0933 ± 0.0371 μg/dl in the L group. These levels were significantly different (p=0.003). Dogs with low sociality per their behavioral assessment had higher cortisol concentrations when interacting with unfamiliar people, compared to their counterparts with higher sociality. This indicates that dogs with low sociality may engage in inappropriate behavior by being overly stressed by unfamiliar people and environments. Sociality constitutes a lifelong characteristic that is formed during puppyhood, which is the period of dog socialization, and is also influenced by the dogs innate character. As such, it is important for owners to encourage dogs to positively accept a diverse range of people and environments during socialization periods. Dogs with positive socialization are better able to manage stress caused by diverse environments throughout the course of their lives, and it appears likely that behavioral problems caused by low sociality can be prevented. Lastly, this study evaluated the stress experienced by dogs in pet drying rooms (PDR

PDR-20000S, Izu Korea, Seoul, Korea), in order to evaluate whether this convenient method for drying dog hair would lead to lower stress compared to common pet dryers (CD

APST2031, A-plus ENC, Incheon, Korea). Drying dogs hair is an essential part of caring a dog

however, the excessive noise and heat may lead to stress and resulting difficulties in caring dogs. The cortisol level after the drying was 2.29 ± 0.30 times greater than that before the drying with CD and 1.21 ± 0.09 times greater with PDR. This ratio of the concentration was significantly different between the groups (p<0.005). Likewise, the concentration after drying increased 0.30 ± 0.07 μg/dl more than that before drying with CD and 0.07 ± 0.03 μg/dl with PDR. There was significant difference between them (p<0.05). For the reason, PDR found to induce a low level of stress compared to CD, and could be useful in large-scale dog facilities due to improved efficiency and lower costs. It is expected that the results from this study will aid in evaluating the welfare of dogs by measuring the stress levels of companion dogs in various environments, and will provide a fundamental basis for stress management in dogs.

Stress is an important indicator of animal welfare. Considering the welfare, as well as the physical health of domesticated animals, is an important perspective in animal health, and determining the appropriateness of particular situations or environments for animals is becoming an important topic of discussion. The level of stress experienced by animals can be comprehensively evaluated by considering their behavioral responses, physiological changes, and a diverse range of immune responses. In particular, physiological changes can be expressed as relatively accurate numerical values, which makes this an objective indicator of stress. Among the physical changes associated with stress, cortisol concentrations are regarded as a trustworthy indicator of immediate stress responses. Especially, the use of salivary cortisol concentrations is on the rise, given the relatively noninvasive nature of such measurements. A diverse range of behavioral problems are being reported in companion dogs. Among such problems, separation anxiety (SA) is very common. Separation anxiety constitutes a representative behavioral issue that often leads to non-adoption, abandonment, and abuse, and requires a combination of chemical therapy and behavioral modification therapy. It is important to prevent unmanaged stress from increasing exponentially. For this reason, this study evaluated whether separation anxiety-induced cortisol concentrations could be lowered through exposure to the smell and voice of the owners. Twenty-eight dogs with SA were divided into three groups and their salivary cortisol concentration along the period (PRE: pre-separation period

SP1–4: separation period

POST: post-separation period) were assessed: group 1 (control), group 2 (with owners clothes during the separation period

SP) and group 3 (a recording of the owners voice was played during SP). In group 1, the cortisol at SP1 was 1.68 ± 0.27 times greater than that at PRE and 2.99 ± 0.50 times greater than at POST. In group 2, The cortisol level at SP1 was 1.17 ± 0.11 times greater than that at PRE and 2.06 ± 0.41 times greater than at that at POST. In group 3, The cortisol level at SP1 was 1.10 ± 0.18 times greater than that at PRE and 1.62 ± 0.14 times greater than that at POST. The ratio of the concentration at SP1 to that at PRE (SP1/PRE) was significantly different among groups (p<0.05). Likewise, the ratio (SP1/POST) differed significantly among groups (p<0.01). In addition, when comparing the differences in concentrations between PRE and SP1 among groups (SP1 – PRE), these levels were significantly different (p<0.05). In the same manner, the differences in concentrations between POST and SP1 among groups (SP1 – POST), there were significant differences (p<0.05). The results indicated that exposing dogs to the smell and voice of their owners could significantly reduce the increase in dogs physiological stress levels in response to separation. As such, we recommend the collection of dog owners smell and voices as a method of managing stress, along with other known techniques. Moreover, this study also evaluated whether low sociality could lead to increased stress caused by exposure to unfamiliar people and environments, ultimately leading to ethological issues. The differences in the sociability and physiological stress response of dogs were evaluated. A total of 37 healthy dogs (21 companion dogs = C group