This experiment examined the effects of positive human contact at suckling on the first day of life on the behavioural and physiological responses of piglets to both humans and routine husbandry procedures. Forty litters from multiparous sows were randomly allocated to one of two treatments: Control (CC, minimal human interaction with day-old piglets) or Positive Contact (PC, human talking and caressing piglets during 6 suckling bouts on their first day of life, day 1). In each litter, 2 males and 2 females were randomly selected and their behavioural responses to tail docking (day 2), and to an experimenter (day 35) were studied. Escape behaviour at tail docking was assessed according to intensity (on a scale from 0 to 4 representing no movement to high intensity movement) and duration (on a scale from 0 to 3 representing no movement to continuous movement). At day 15 of age, a human approach and avoidance test was performed on focal piglets and at day 15, escape behaviour to capture before and after testing was recorded again. Blood samples for cortisol analysis were obtained from the focal piglets 30 min after tail docking and 1 h after weaning. Escape behaviour to tail docking of the PC piglets was of shorter duration than that of the CC piglets (P = 0.05). There was a tendency for the escape behaviour both before and after testing at day 15 to be of a lower intensity (P = 0.11 and P = 0.06, respectively) and a shorter duration (P = 0.06 and P = 0.08, respectively) in the PC piglets. There was a tendency for PC piglets to have higher cortisol concentrations after tail docking than the CC piglets (P = 0.07). Male piglets had higher cortisol concentrations after tail docking and after weaning than female piglets (P = 0.02 and P = 0.03). The results indicate that Positive Contact treatment reduced the duration of escape behaviour of piglets to tail docking. The role of classical conditioning, habituation and developmental changes in the observed effects of the Positive Contact treatment is unclear. Nonetheless, this experiment demonstrated that brief positive human contacts early in life can alter the behavioural responses of piglets to subsequent stressful events.
Keywords: Behaviour; Human contact; Learning; Physiology; Stress.