부산대학교 도서관

Simple Summary: We explored the application of infrared thermography (IRT) as a non-invasive method to measure the eye's lacrimal caruncle temperature in sheep, specifically focusing on its potential to detect negative emotions such as fear. Fourteen ewes, divided into two study groups according to the exposed emotional (positive n = 7 and negative n = 7), were subjected to classical conditioning associating a neutral auditory stimulus with either a positive event (food reward) or a negative event (opening an umbrella). Then, lacrimal caruncle temperatures using IRT, behavioral observation of ear postures, and saliva samples were collected to assess cortisol levels at rest and after treatment. The results reveal a significant increase in lacrimal caruncle temperature post-treatment only in the negative group (p = 0.017), indicating a potential association between IRT-measured eye temperature and negative emotional states in sheep. Additionally, behavioral observations align with the learned association between the neutral stimulus and events of different emotional valence. As for cortisol, despite not being significant, its levels increased for both groups post-treatment. The study concludes that IRT proves valuable in non-invasively evaluating the physiological impact of positive and negative events on sheep. Infrared thermography (IRT) has been recently applied to measure lacrimal caruncle temperature non-invasively since this region is related to the sympathetic response, and it seems a promising technique that is able to infer negative emotions in sheep (e.g., fear). However, the scientific literature so far is limited in understanding whether a caruncle's temperature changes also in response to positive emotional states in sheep. Through classical conditioning, we aimed to assess how a positive or a negative event affects the physiological (lacrimal caruncle temperature measured with IRT and cortisol levels) and behavioral responses of sheep (ear position). Fourteen ewes from the same flock were randomly assigned to two treatment groups: positive (n = 7) and negative (n = 7). Each group was then trained through classical conditioning to associate a neutral auditory (ring bell) stimulus to an oncoming event: for the positive group, the presence of a food reward (maize grains), while for the negative one, the opening of an umbrella. After three weeks of training, before (at rest) and after (post-treatment), lacrimal caruncle temperature was non-invasively measured via IRT, and saliva samples were gently collected to measure cortisol levels. During treatment, sheep behavior was videorecorded and then analyzed using a focal animal sampling technique. At rest, the eye's lacrimal caruncle temperature was similar in both groups, while post-treatment, a significant increase was shown only in the negative group (t-test; p = 0.017). In the anticipation phase, sheep in the positive group kept their ears forward longer compared to those in the negative one (Mann–Whitney; p < 0.014), 8.3 ± 2.1 s and 5.2 ± 4.2 s, respectively. The behavioral response observed reflects a learnt association between a neutral stimulus and events with different emotional valence. Cortisol concentration slightly increased in both groups post-treatment. Our results confirm that IRT is a non-invasive technique that can be useful when applied to assess how positive and negative events may affect the physiological response in sheep. [ABSTRACT FROM AUTHOR]