Effect of tickling and gentling on eye and tail temperature of laboratory rats during manual restraint, using infrared thermography.

Abstract

Laboratory rats can experience acute stress during handling procedures, which can negatively affect animal welfare. The purpose of this research was to investigate if rats that had been regularly tickled or gentled from a young age experienced less acute stress during manual restraints due to the social buffer effect these procedures may provide. As read-out parameters for stress levels, maximum eye temperature and mid-tail temperature were used to reflect the stress-induced hyperthermia. Sixteen male Wistar rats (WU:Crl) with an age of three weeks at arrival in the lab were included in this study. Maximum eye temperature and mid-tail temperature were measured before, during and after a stressor period containing several manual restraints, using a FLIR T430sc thermal camera. Due to limitations, no reliable measurements were made for the eye temperature experiment and were, therefore, excluded from the results. For the mid-tail temperature, results showed that the gentled rats (G, n = 4) had a lower baseline tail temperature than the tickled rats (T, n = 8), where the control group (CONTROL, n = 4) showed the highest baseline temperature. During the stressor period, the tail temperatures of all rats dropped to a comparable lowest point temperature, suggesting repeated manual restraint is a stressful experience for all rats. Differences in temperature between the treatment groups during this period could not be distinguished, due to the differences in baseline temperature. Without additional parameters to assess stress levels and a behavioral study, no conclusions for this study could be made yet. However, future research may confirm the suggestion that tickling and especially gentling rats may positively affect animal welfare by improving the human-animal bond, lower the general fear of humans, decrease stress levels during manual restraints, and maybe lower chronic stress levels.