Proposal of a Grimace scale in goat kids

Abstract

The analysis of facial expressions through the Grimace scales has become an increasingly developed tool to determine the degree of animals’ pain. The aims of this preliminary study were to prove if there were any differences between the facial expressions of healthy and sick goat kids by observing the most common facial action units in this species and to create a Goat kid Grimace Scale. Sixty 0 to 20-day old Majorera goat kids from three different livestock farms were used for this study. Twenty animals in no pain, twenty animals in moderate pain and twenty animals in severe pain were chosen and two photographs were taken of each animal's face, one from the front and one from the right profile. Three facial action units were analysed: orbital tightening, nose features and mouth features and these were objectively measured using different software. Statistical analysis was performed using RStudio. Eye Index and Front Nose Angle were non normal distributed (P = 0.024 and P = 0.001, respectively), and Mouth Angle and Profile Nose Angle were normal distributed (P = 0.559 and P = 0.258, respectively). Pearson correlation analysis showed a medium negative correlation between pain degree and Eye Index (r = -0.50). The effect of pain degree on Mouth Angle, Eye Index and Front Nose Angle was statistically significant (P = 0.013, P = 0.001, and P = 0.009, respectively) but the effect of pain degree on Profile Nose Angle was non statistically significant (P = 0.133). The results of this preliminary study corroborate the idea of that goat kids’ facial features change accordingly with pain degree, but it is necessary to refine the research technique and increase the number of animals recorded.