Disentangling the effects of weaning stressors on piglets’ behaviour and feed intake: Changing the housing and social environment

Abstract

Under farming conditions piglets generally face several simultaneous stressors including separation from the dam, an abrupt change from milk to a solid diet and changes in the social and housing environments. In this study we tested the hypothesis that increasing the number of environmental stressors imposed at weaning would intensify the behavioural distress response and reduce feed intake and weight gain short-term post-weaning. At 21 days after birth, piglets were weaned following one of the treatments: T1 – the dam was removed and the entire litter was left in the farrowing housing; T2 – the entire litter was moved to a pen in a nursery room without mixing with unfamiliar animals; T3 – piglets of two litters were mixed and moved to similar pens in a different nursery room ( n = 8 groups/treatment). Pens were videotaped for 10 consecutive days post-weaning and used for behavioural analysis; vocalizations were recorded by direct observation on day 0 (weaning day) and day 1; the proportion of piglets with skin lesions was assessed on days 1 and 6; piglets were weighed and feed intake was recorded daily. Overall feed intake was highest in T1 than in T2 and T3 litters ( P < 0.008). Body weight did not differ ( P > 0.05), but body weight gain between weaning and day 9 was greater in T1 than in T3 ( P < 0.01). Compared to the two other groups, T3 group had higher frequencies of agonistic and exploratory behaviours, lower resting frequency and a higher proportion of piglets with severe skin lesions ( P < 0.05). Frequency of vocalizations was similar in T2 and T3, but both were higher than in T1 litters ( P < 0.001), in which calls were observed only occasionally. This study shows that increasing the number of environmental stressors at weaning exacerbates the distress response of 21-day-old weaned piglets. It also suggests that some commonly reported responses, like an increase in aggression, activity and vocalizations, are mostly associated with exposure to unfamiliar social and spatial environments, rather than the loss of the dam.