Repeated transport and isolation during pregnancy in ewes: Effects on the reactivity to humans and to their offspring after lambing

The aim of this study was to determine if repeated exposure to stressors of a different nature and intensity during the last 6 weeks of pregnancy modifies the reactivity of ewes to their lambs and to humans after lambing. Multiparous ewes were either subjected to 10 sessions of transport in isolation twice a week for 1 h (TRAN, n = 20 ewes), 10 sessions of isolation with or without the presence of a dog twice a week for 1 h (ISOL, n = 20 ewes) or no disturbance (CON, n = 19 ewes). Blood samples were collected during the 1st, 5th and 9th stress sessions for the TRAN and ISOL ewes and cortisol responses were measured. Maternal reactivity and fear of a human were measured during several challenge situations: 1 h after parturition (1) a human approached the lambing site at tagging and (2) a human held the lambs; 6 h after parturition, (3) the ewe was forced to cross a corridor to reach its lambs, (4) the ewe was forced to tolerate the presence of a human if it wished to remain close to its lambs and (5) the ewe was separated from its lambs; 1 month after parturition (6) a human approached the ewe and (7) the flight distance in response to a human was measured. A Principal Component Analysis was used to identify groups of statistically interrelated measures which otherwise would have remained undetected. During the 1st and the 9th sessions, transport in isolation provoked a greater cortisol release in ewes than isolation alone. However, ewes from both treatments habituated to the treatment with time. During the tests performed 1 h and 6 h after parturition, a clear divergence in reactivity was observed between treatments: ISOL ewes tried to maintain contact with their lambs in the presence of a human while TRAN ewes did not. CON ewes showed an intermediate response between ISOL and TRAN ewes. The divergence in behaviour persisted 1 month after parturition with ISOL ewes showing less avoidance of a human than TRAN ewes, CON ewes were intermediate. Correlations were found between cortisol responses and behavioural responses during the tests performed 1 h, 6 h and 1 month after lambing. The differences in ewe behaviour during challenge situations after lambing were probably not due to a weaker mother–young bond but to divergence in the effect of treatment during pregnancy on fear of humans: repeated isolation reduced fear of humans whereas repeated transport increased it.