Farmer Perceptions of Pig Aggression Compared to Animal-Based Measures of Fight Outcome.

Most farmers do not perceive pig aggression to be a problem that needs to be addressed, despite the fact that stress and injuries are common and a number of management strategies have been identified. This study investigated whether routine exposure to pig aggression disrupts farmer responses to aggression. Pig farmers (n=90) were shown video clips of pigs immediately after a dyadic contest (clips 1-3) and during a contest (clips 4&5). Video footage was obtained from a separate research project whereby 168 growing pigs were video recorded in aggressive encounters. For each pig measures of skin lesions (injury) and blood lactate (physical fatigue) were taken pre- and post-fight to indicate relative change as a result of aggression. A stepwise selection process was used to choose each video clip. Based on the severity of skin lesions and blood lactate we identified from the entire dataset the encounters whereby both pigs obtained low (lower quartile, clip 1), medium (interquartile range, clips 2, 4&5) or high (upper quartile, clip 3) severity measures. Participants viewed all clips, and the order was randomised in each session. Following each clip, farmers were asked to place a downward line through 100mm visual analogue scales at a point they felt best represented: i) how much of a negative emotional reaction they had; ii) how exhausting they believe the fight was; and iii) how severe they believed the fight was. Their judgments were compared to the objective measures of severity, and against control groups with similar pig experience (10 pig veterinarians) and without experience (26 agricultural students; 24 animal science students) of working with pigs. Famers did not show desensitization to aggression; they expressed greater emotional response scores (mean=45.6, SE=1.5) and judged fight exhaustion (mean=55.7, SE=1.5) to be higher than agricultural students (emotion: mean=38.3, SE=2.3; exhaustion: mean=49, SE=2.4) (p <0.05).However, all groups underestimated the severity of aggression when they saw pigs after the contest had ended as compared to witnessing a fight in progress. All participants scored emotional response, exhaustion and severity as greater for both of the ‘during fight’ clips than for the ‘post-fight’ clips (p < 0.05), even when post-fight outcomes were severe as indicated by objective measures. Farmers are unlikely to witness fights as frequently as they actually occur. They are expected to witness the injuries from such interactions during their regular inspections; however results suggest that they are unlikely to fully recognize these outcomes. We recommend that farmers are made aware of how to accurately determine the physical impact of aggression by scoring skin lesions on affected animals. Furthermore, researchers should calculate the economic and welfare impact of aggression as indicated by the lesions. All human and animal experimentation conforms with the ISAE Ethical Guidelines