Neurological modulation of facial expressions in pigs and implications for production

Abstract

The facial expressions of animals constitute a means of manifesting emotions, fulfilling functions related to social interactions in several species. Interest has come to use facial expressions as a tool for predicting intentions; in the case of aggression, for example, impeding attacks between individuals prevents negative economic and emotional impacts. Recent research has sought to associate facial expressions with painful events as tail-cropping and castration on the assumption that objective evaluations of the presence or absence of grimaces in pigs’ snouts may allow us to determine the intensity of the pain they perceive. Furthermore, to continue developing scales that will complement the existing piglet grimace scale (PGS), which is not yet fully-validated in terms of reliability. Another area of research is interpreting expressions of fear during traumatic events like pre-slaughter handling. Also, the phenomenon of emotional contagion in groups of animals suggests the need to focus on their emotions, since recognizing them could allow us to prevent alterations of meat quality. These approaches reveal the need for a detailed compilation of the facial expressions of pigs based on current scientific literature regarding emotions, alimentation, and pain-related behavioral responses in pigs.