Christine Pelland from Southwest Ontario Veterinary Services, Animal Aggression: Do We Get Desensitized To Negative Outcomes Over Time?



Aggressive behaviour is a natural occurrence in pigs. Even though aggression it is a natural behaviour it does not make it desirable behaviour when it comes to optimizing the welfare of the pig. The injuries that result from aggressive behaviour can reduce profitability. While it is obviously not practical to eliminate all aggression there exist a number of management strategies that can reduce this “bad behaviour”. For example, allowing litters to mix prior to weaning, housing pigs in large social groups, and enhancing levels of tryptophan in the feed have all been demonstrated to reduce the occurrence or intensity of aggression at  regrouping. Unfortunately, these interventions can be labour intensive, add to the cost of production or both.

UK researchers wanted to know if frequent exposure to animal aggression could affect how

farmers would respond to distressed animals. Perhaps farmers might be getting desensitized to the situation because of ongoing exposure of the farmer to the aggressive behaviour. The researchers had 90 pig farmers rate the severity of aggression, level of pig exhaustion and the strength of their own emotional response to the aggression. The farmers judgments were then compared to objective measures of severity including the assessment of the pigs’ skin lesions and blood lactate. The researchers carried out the same rating for 10 pig  veterinarians. Finally, they looked at the response in 26 agricultural students and 24 animal science students that had not worked in pig farms for a significant duration.

The researchers found that the famers did not show desensitization to aggression. Their ratings were similar to the control group. In fact, the older farmers tended to be even more empathetic to the outcomes of aggression than average. Women also tended to be more empathetic. All groups in this study did however underestimate the outcome of aggression when they did not witness the actual fight in progress and based their observations only on the skin lesions.

Take Home Message

There was no evidence that farmers became desensitized to the negative effects of animal welfare concerns associated with aggressive behaviour although.

There was evidence to suggest that seeing a fight in progress provides the greatest  impression on farmers rather than assessing lesion scores after the fact. Farmers can’t be “omnipresent” and they are not always going to be around to monitor the aggressive behaviour while it is in progress. Farmers might benefit from additional training that would “connect the dots” between the skin lesions caused by aggression and the economic and welfare impact of that aggression.

Submitted by Christine Pelland, DVM



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