# Mixed Management in Growing and Finishing Pigs: Impacts on Social Behavior and Judgment Bias

## TL;DR

This study shows that mixing unfamiliar pigs and their gender affects their behavior and decision-making, which can help improve farming practices.

## Contribution

The study reveals gender-specific differences in judgment bias and behavior in pigs under social stress, offering new insights for welfare management.

## Key findings

- Females showed more fear and caution in unfamiliar situations compared to males.
- Females exhibited pessimistic judgment during ambiguous cues in the judgment bias test.
- Repeated mixing of pigs influenced their social and non-social behaviors differently based on gender.

## Abstract

Understanding how pigs respond to social and environmental challenges is essential to improve their welfare in farming systems. In this study, we investigated how mixing unfamiliar pigs and testing them in different contexts influenced their behavior and cognitive responses. Ninety-six pigs were allocated to groups, with some experiencing social stress by being mixed with unfamiliar conspecifics. We evaluated open field, food motivation, and judgment bias tasks. Gilts showed more signs of fear and caution in unfamiliar situations than barrows, taking longer to interact with food and to complete learning tasks. These results suggest that both previous social stress and sex can affect how pigs explore and make decisions. Such insights can guide improvements in welfare-oriented management on commercial farms.

Intensive pig production practices may shape cognition and behavior. We evaluated whether repeated regrouping (mixing) and gender (gilts vs. barrows) affect social interactions, fear-related responses, and affective state. A total of 96 growing pigs were separated into two treatments: control—pigs that were mixed once during the growing–finishing period; and social stress—pigs that were mixed thrice during the growing–finishing period. Social and non-social behaviors were directly noted, and four behavioral tests were conducted: open field, novel object, couples, and judgment bias tests. The statistical analysis compared gender and treatment, and p-values ≤ 0.05 were considered significant. Females stayed longer in the test pen entrance area during the novel object test and barrows spent more time at the feeder and defecated more during the couples’ test. With regard to the judgment bias test, females took longer to be considered trained in the discriminatory learning task and presented a “pessimistic judgment” during the ambiguous cue. Our results suggest that gender influences judgment bias in pigs and can influence social and non-social behavior, which may reflect a negative affective state with implications for their welfare and management.