Temporal stability of personality traits in group-housed gestating sows

The movement of sows (Sus scrofa domesticus) out of individual gestation stalls and into group housing can introduce new sources of stress due to the enhanced environmental and social complexity. Some sows may have the behavioral capacity to adapt to these changes better than others. However, little is known about individual differences in behavioral responses, or personality traits, in gestating sows and how they impact the animal's ability to cope with group housing. The temporal consistency in the assessment of an animal's behavior is a prerequisite to the establishment of personality traits and was addressed at an interval of approximately five months during two consecutive gestation periods in the present study. Forty-six group-housed sows from a commercially available genetic line were assessed for aggressive and social behaviors at mixing into a group, reaction to human approach, ease of handling, exploration of an open field, and reaction to a novel object. Principal component analysis revealed the presence of three traits accounting for over 60% of the variance in behaviors: aggressive/dominant, avoidant of humans and active/exploratory. Individual component scores were significantly correlated between pregnancies demonstrating temporal stability of trait assessment. Significant relationships were found between aggressive/dominant component scores and individual feed rank at electronic sow feeding stations and skin lesion scores, as well as between avoidant of humans component scores and average number of stillbirths per litter. These findings provide evidence for the temporal stability of distinct behaviors contributing to personality traits within a group of genetically similar sows and demonstrate how these traits may be useful in identifying individuals likely to succeed in group housing.