Repeated handling of pigs during rearing. I. Refusal of contact by the handler and reactivity to familiar and unfamiliar humans

Abstract

Pigs housed in groups received different handling treatments for 40 d until slaughter age. Pigs of the human interaction (HI) and refusal of contact (RC) groups were individually introduced into a pen each day, where they remained for 3 min in the presence of a squatted handler. The handler tried to increase progressively physical reciprocal interactions with the HI pigs using eye and body contact and voice. The handler remained immobile and avoided eye contact and use of voice with RC pigs. These pigs were pushed away when they touched the handler. Control pigs remained in their home pens. Over sessions, HI pigs progressively increased physical interactions with the handler, up to 35% of their time. The RC pigs were motivated to interact with the handler as they tried to establish physical contact with the handler throughout the experiment. They increased levels of locomotion, rubbing, immobility, and snout contact with the wall, suggesting that they were frustrated by the refusal of contact. At the end of the experimental period, all pigs were subjected to three human exposure tests, where pigs were exposed to the handler and two other persons, one of which was unfamiliar, in a Latin square design. During this test, behavior of the humans was the same as for the RC treatment. The HI pigs discriminated between the handler and the other persons as indicated by their increased approach behavior towards the handler. Part of the prior handling experience was generalized to other humans as indicated by higher levels of proximity of HI and RC pigs with the different persons compared with controls. Physical contact with the human was associated with increased heart rates. Two possibilities are that these two characteristics are part of a general behavioral/physiological reactive profile, or that contact with humans provokes an arousal or emotional response. Despite this, behavioral data show that pigs are motivated to be in physical contact with a handler, even when the handler consistently refuses contact.