Interpretive Summary: Time budgets of group-housed pigs in relation to social aggression and production

By: Anne Kamiya, MS

Eliminating gestation crates allows pigs to be group-housed so they can express more natural behaviors. However, managing group-housed pigs is very challenging. Pigs fight with unfamiliar pigs until they establish a social hierarchy. Aggression can lead to increased stress, poor health and reduced growth performance. Therefore, minimizing social aggression when introducing pigs is an important animal welfare issue.

In this recent Journal of Animal Science study, pigs were observed over specific time intervals to create “time budgets” associated with specific behaviors. It was hypothesized that newly introduced pigs would spend more time on aggressive behaviors and exploring their new environment.

Castrated male pigs were group-housed at 10 weeks of age and observed for behaviors at introduction and again at 3, 6 and 9 weeks after introduction. “Time budgets” for specific behaviors were created based on these observations. Behaviors were categorized as follows: aggression, exploration, inactive, ingestion, movement and social. Aggression was high at introduction but significantly lessened over the 9 weeks. Pigs mostly spent their time inactive, but inactivity increased from introduction to 9 weeks. No significant impacts on production were noted. The authors stated that throughout the entire study period, aggression was negatively correlated with all other activities. The authors suggest that promoting nonaggressive behaviors such as exploration and movement may reduce aggression after the introduction period.

Overall, the results of this study document how newly introduced male pigs spend their time over the first nine weeks. The authors’ suggestion that promoting other non-aggressive behaviors to reduce aggression are valid, but require further study—e.g., at what point and how should such interventions be introduced? Studies on behaviors, social aggression and time budgets of female pigs is a recommended area of future study.

The full article can be found on the Journal of Animal Science website.