Fig 1.
The photographs were taken at the time points in boxes. The black and white boxes are time-matched (TB2 was used as a baseline for T2 and TP2, while TB5 was used as a baseline for T5 and TP5).
Table 1.
Time schedule of the 7-part survey with the scores that were assigned to the photographs of the ferrets.
AU1-5 = action unit 1–5 of the Ferret Grimace Scale (orbital tightening, nose bulging, cheek bulging, ear changes and whisker retraction), presented in random order. Pre-training = intuitive overall pain assessment, post-training = overall pain assessment after being trained on the Ferret Grimace Scale.
Fig 2.
Skin and superficial muscles were removed during dissection, drawing made by R. van Deijk.
Table 2.
Name, origin, insertion and action of the facial muscles of the ferret [30].
Fig 3.
Photographs visualizing the normal appearance and changes (0 = not present, 1 = moderately present, 2 = obviously present) of the five Action Units that are used in the Ferret Grimace Scale.
Table 3.
Number and percentage of pictures (N = 209) that were scored ‘I not to know’ for orbital tightening, nose bulging, cheek bulging, ear changes, whisker retraction and overall pain pre- and post-training by 11 observers of 19 ferret faces at different time points (TB2, TB5, T2, T5, TP2 and TP5).
Fig 4.
Average percentage of ferrets (N = 19) that were assigned score 0, 1, and 2 for each of the AUs in the FGS by 11 observers at different time points.
a) orbital tightening, b) nose bulging, c) cheek bulging, d) ear changes and e) whisker retraction on six time points relative to the time of surgery (T0), * = score is significantly different from score on TB2, # = score is significantly different from score on TB5 with p<0.05 (11 observers, 19 ferrets).
Fig 5.
Obtained by performing the LDA on the observer scores for orbital tightening, nose bulging, cheek bulging, ear changes and whisker retraction. a) using all AUs, b) without whisker retraction.