Abstract
This study was conducted in a Portuguese slaughterhouse for finishing pigs. A total of 93 batches with an average slaughter weight of 93.3 kg (±0.6) were assessed in the lairage pens using the qualitative behavior assessment (QBA) tool to evaluate both positive and negative descriptors. Social interaction behaviors and the physical conditions of pigs in each batch were also measured. Physical examination revealed that pigs with body condition scores of 4 or 5 were less active and playful, presenting negative correlations with these descriptors. Groups of pigs at rest showed negative correlations (p < 0.001) with active (r = -0.338), lively (r = -0.352), and playful (r = -0.424) behaviors, while resting behavior was positively correlated (p < 0.01) with relaxed groups (r = 0.331). The presence of fighting and mounting the backs of other animals was highly correlated (p < 0.001) with negative emotional states like agitation, distress, irritability, and tense. Batches exhibiting positive emotional states, such as calmness and relaxation, showed significant associations with behaviors like fighting and mounting the backs of other animals. This indicates that experiencing positive emotions can lead to a decrease in aggressive or stress-related behaviors. Ear biting correlated with the descriptor "bored", indicating a potential relationship between this behavior and a lack of environmental stimulation. The descriptors "frustration" and "bored" (p < 0.001) showed an association with the behavior of chewing without a substrate, regardless of whether fights occurred. Descriptors like "active", "friendly", "positively occupied", "sociable", and "lively" have higher loadings on principal component 1 (PC1), reflecting positive affective welfare. In PC2, descriptors representing relaxation are positioned as opposite to terms like "irritable", "distressed", and "tense", suggesting that PC2 could be useful for identifying conditions of high stress in pigs. These findings underscore the relationship between emotional states and behaviors, suggesting that combining QBA with behavioral observations provides a comprehensive framework for assessing animal welfare. Improving pig welfare could be achieved by reducing aggression and enhancing environmental enrichment to alleviate boredom during lairage.