Measuring positive emotions in free-range sheep using peripheral temperatures, facial action units and ear postures

Abstract

The purpose of this study was to elucidate the effect of stroking ewes’ body as a positive emotional stimulant on peripheral temperatures, facial action units and ear postures. Thirty-eight healthy ewes were included in the current study. The animals were stroked individually on neck, withers and fore-head. Then the procedure was divided into three stages: pre-stroking, stroking and post-stroking with five minutes each. Peripheral temperatures were measured from eye, nose and ear using infrared thermal camera. Images were also captured to analyse facial units in studied sheep. For measuring head behaviours and ear postures, the ear change as a frequency per minute was measured at 30-second intervals for 15 respective minutes. During stroking, the temperature of eye, ear and nasal areas has significantly dropped (P<0.05), however it raised in eyes during the post-stroking period. Significant differences (P<0.05) were also found between pre-stroking and post-stroking phases in ear and nose temperatures. For facial units, significant differences (P<0.05) were found between pre-stroking, compared to stroking and post-stroking phases for all five facial units. In addition, the total facial action score was significantly (P<0.05) higher during the stroking and post-stroking phases, compared to the pre-stroking phase. Results obtained from ear positions showed that the time spent with ears in plane position had significantly decreased (P<0.05) in the stroking phase compared to pre- and post-stroking phases. In addition, ewes spent more time with their ears backward (P<0.05) during stroking in comparison to pre- and post-stroking phases. No significant differences were found in asymmetrical and forward ear postures. In comparison to the pre-stroking stage, the number of ear position change was not significantly increased during stroking, however, it increased considerably (P<0.05) in the post-stroking period. From this study, it was concluded that stroking ewes’ body parts improved significantly the positive emotional state in healthy animals.

Keywords

• facial expressions
• peripheral temperatures
• positive emotions
• sheep
• stroking