Title : Quantifying changes in facial expression following hot-iron disbudding under procaine hydrochloride and meloxicam treatment in Holstein dairy calves
Abstract:
The analysis of facial expression for cattle pain assessment has been under explored compared to other animal species, despite reports highlighting its usefulness. Therefore, this study aimed to assess changes in facial expression following hot-iron disbudding, a routine painful procedure, in dairy calves. Seventeen female calves (4.59 ±0.27 weeks old) were divided into two groups: A (n=11), to be disbudded and B (n=6), the control. Video recordings (two mins each) were obtained immediately prior to disbudding in both groups and following disbudding in group A only. Still images were extracted from each video at thirty secs intervals resulting in four images/calf in group B and eight images/calf in group A. Images were randomly arranged and used to create an online survey which assessed participants’ ability to recognise and score facial expression based on six action units (AUs): backward ear-BE, nose bulge-NB, eye closure-EC, cheek tense, tongue show, and open mouth and/or upper lip raise. The survey was first piloted before recruiting 196 participants using mixed sampling methods. Participants were provided with the survey link containing participant information sheet, consent form, pictorial guide of the AUs associated with disbudding and calf facial images to be scored on a three-point scale (0 =not present, 1 = moderately present, 2 = obviously present. If the participants were unable to score an AU clearly, they were asked to use the ‘don’t know’ option. The total sum of AU (TSAU) scores/calf and mean score of each AU/calf were compared within and across groups using paired and independent sample t-test, respectively. Post-disbudding, the TSAU score was significantly higher than the pre-disbudding mean (P = 0.001) and the control (P = 0.001). Mean scores of BE (P = 0.037) and EC (P = 0.010) were significantly higher than pre-disbudding. Compared with the control, BE (P = 0.048) and NB (P = 0.021) were significantly higher post-disbudding. These findings suggest that changes in facial expression occur following disbudding, and quantification of these changes may be useful for optimising pain management in disbudded calves.
