Document type: scientific article published in Animal
Authors: I. Reimert, G.A. Franchi, M. Bagaria, L. Canario, J. Elizabeth Bolhuis, S. Düpjan, E. Verbeek, E. Fàbrega, L.J. Pedersen, H. Telkänranta, A. Eggert, L.R. Moscovice
Abstract in French (translation): Collaboration for Animal Welfare: An Interinstitutional Approach to Identifying Reliable Indicators of Emotions in Pigs,Animal
Assessing emotions in farm animals is challenging due to their subjective nature and the lack of reliable indicators, particularly for positive emotions. We developed experiments conducted at four facilities, all designed to elicit positive and negative emotional responses in n = 124 domestic sows tested using an intra-subject protocol. Our objectives were to test reliable and noninvasive indicators of short-term emotional responses in pigs representing different ages and breeds and raised under various farming conditions. We developed a common ethogram for behavioral recording as well as standardized operating procedures for collecting saliva samples, which were analyzed in the same laboratory to measure short-term variations in cortisol—as an indicator of arousal—and oxytocin—as a putative indicator of valence. We used linear models and generalized linear mixed models (LMM/GLMM) to test the effects of predicted differences in valence and arousal across the different experiments on behavioral and physiological responses. We also conducted a multilevel principal component analysis (PCA) to determine whether multiple indicators could be grouped into a smaller set of principal components representing different dimensions of emotional responses. The most consistent indicators varied as expected across facilities, with an increase in locomotor play in positive contexts (GLMM, P ≤ 0.001) and an increase in escape attempts in negative contexts (GLMM, P ≤ 0.001). Pigs were more likely to have both ears pointed forward in positive contexts (GLMM, P ≤ 0.001) and both ears pointed backward in negative contexts (GLMM, P ≤ 0.001). The pigs exhibited greater increases in cortisol in response to negative-valence contexts than to positive-valence contexts (LMM, P ≤ 0.001); furthermore, regardless of valence, pigs exposed to more novel social or physical contexts during the experiments also exhibited greater increases in cortisol (LMM, P ≤ 0.001). Oxytocin levels did not show consistent variations across contexts of different valence. The pigs’ PCA scores clustered according to the contexts of different valence they had experienced, rather than according to their different housing locations. The two principal components with the highest eigenvalues exhibited moderate loadings for a combination of more established indicators and new indicators related to fear responses as opposed to playful responses. In conclusion, this interinstitutional approach validated the use of locomotor play and flight behavior as reliable indicators of short-term valence responses within pig populations. When combined with other measures, short-term changes in ear posture also constitute a promising valence indicator. Cortisol variations were related to both valence and arousal. Interinstitutional approaches are useful for strengthening the validity of noninvasive indicators of emotions in farm animals.
Preview: Evaluating emotions in livestock is challenging due to their subjective nature and the lack of robust indicators, especially for positive emotions. We developed experiments across four facilities, all designed to induce positive and negative emotional reactions in n = 124 female domestic pigs tested in a within-subject design. Our goals were to test for robust, non-invasive indicators of short-term emotional responses across pigs representing different ages and breeds and kept in different husbandry conditions. We developed a common ethogram for behavioural recording and standard operating procedures for collecting saliva samples, which were analysed in the same lab to measure short-term changes in cortisol, as an indicator of arousal, and oxytocin, as a putative indicator of valence. We used linear and generalised linear mixed models (LMM/GLMM) to test for effects of predicted differences in valence and arousal across different experiments on behavioural and physiological responses. We also ran a multilevel principal component analysis (PCA) to assess whether several indicators could be consolidated into a smaller set of principal components representing different dimensions of emotional responses. More established indicators varied as predicted across facilities, with increases in locomotor play in positive contexts (GLMM, P ≤ 0.001) and increases in escape attempts in negative contexts (GLMM, P ≤ 0.001). Pigs more often had both ears pointed forward in positive contexts (GLMM, P ≤ 0.001) and both ears pointed backwards in negative contexts (GLMM, P ≤ 0.001). Pigs had greater increases in cortisol in response to negatively than to positively valenced contexts (LMM, P ≤ 0.001), and regardless of valence, pigs exposed to more novel social or physical contexts during experiments also had greater increases in cortisol (LMM, P ≤ 0.001). Oxytocin did not vary consistently across differently valenced contexts. Pigs’ PCA scores clustered according to the differently valenced contexts that they experienced and not to their different facilities. The two principal components with the highest eigenvalues had moderate loadings for a combination of more established and novel indicators related to fearful vs playful responses. In conclusion, this cross-institute approach helped to validate the use of locomotor play and escape behaviour as robust indicators of short-term valenced responses across pig populations. When combined with other measures, short-term changes in ear posture also have promise as a valence indicator. Changes in cortisol were related to both valence and arousal. Cross-institute approaches are useful for increasing the validity of non-invasive indicators of emotion in farm animals.
