Maternal contact and positive human interactions during lactation impact on pig stress resilience post-weaning

Abstract

This study investigated the impact of early life interactions on stress resilience of weaner pigs. The hypotheses tested were that reduced maternal contact increases the stress response of pigs to weaning, and that positive human contact during lactation reduces, the stress response of pigs to weaning. Ninety-eight litters were allocated to a 2×2 factorial randomised block design for treatments maternal contact (MC+) / reduced maternal contact (MC-); and positive human contact (HC+) / control (HC-). Modified farrowing crates were used to reduce maternal contact (MC-). Litters in the HC+ treatment received five minutes of daily positive human interaction (stroking). Treatments ceased at weaning (22 days old). Forty-three pigs were mixed into pens of the same treatment at weaning. Behavioral observations were conducted for 2 hours post-weaning and for 4 hours at 2 weeks post-weaning, along with behavioural responses to humans and isolation at 3 and 4 weeks post-weaning, respectively. Cortisol, haptoglobin and IgA concentrations were collected the day prior to weaning at rest, two hours post-weaning, one hour following isolation and at 4 weeks post-weaning and at 5 weeks post-weaning at rest (basal). End weight and survival were also recorded. Results showed that in the first 90 minutes after weaning, HC+ pigs exhibited more inactive behaviours (P<0.05), and less aggressive and eating behaviours (P<0.05) along with more social behaviours (P<0.05) at 90–120 minutes compared to HC- pigs. These findings suggest a quicker stabilisation of behaviour following weaning. While maternal contact did not affect play, aggressive, social or drinking behaviours (P>0.05), MC+ pigs exhibited more eating and active behaviours (P<0.05) from 30 to 60 minutes post-weaning. There were no significant treatment effects (P<0.05) on the physiological measures except at 5 weeks post-weaning where the IgA concentrations of the MC-/HC+ pigs remained steady while those of the other pigs increased five fold (P=0.002). While there were no treatment effects (P<0.05) on the behaviour of pigs at rest at 2-weeks post-weaning, in response to isolation at 4 weeks post-weaning or on performance post-weaning, there was limited evidence that the MC- pigs were less fearful of humans in the test at 3 weeks post-weaning. Based on the behavioural response of pigs immediately following weaning, early positive handling assisted pigs to cope with the stress of weaning. While previous research provided evidence of maternal contact on stress resilience during lactation, the present study provides limited evidence of maternal contact on stress resilience of the weaned pig.