Space allowance during gestation and early maternal separation: Effects on the fear response and social motivation of lambs

A common prenatal stressor in lambs is early maternal separation, which may be aggravated by spatial restriction of ewes during pregnancy. They may influence lambs’ development and coping abilities. The aim of this study was to determine how space allowance provided to ewes during pregnancy and early maternal separation affected the fear response and social motivation of lambs. A total of 54 ewes were randomly assigned to three living areas of 1, 2, or 3m2/ewe (SA1, SA2, and SA3, respectively) during pregnancy. After birth, lambs from each treatment remained with their mothers (MR) or were early separated (ES). In the study 42, 2–3 day old lambs were sequentially subjected to a novel arena, a novel object, and a social motivation test. Information on their behaviour, movement patterns, and vocalizations was collected. Results of the study indicate that ES lambs born from SA1 ewes were more fearful, as indicated by the higher levels of immobility and number of vocalizations during novel arena tests, the latter being also observed during novel object tests (P<0.05). Change of location tended to be less frequent in ES lambs during novel arena tests (P<0.10), while the behavioural response of MR lambs appeared to be more homogeneous and independent from the pre-natal space allowance treatment during the novel object tests. ES SA1 lambs also spent the highest % of time close to other lambs (P<0.05) and performed the highest number of vocalizations during the social test (P<0.05). The fear response of lambs during the novel arena and novel object tests was gender dependent, with females vocalizing more and interacting more frequently with the stimulus during novel object tests (P<0.05). Females also showed higher social motivation than males, but vocalized less (P<0.05). Results suggest that the detrimental effects of early maternal separation might be exacerbated by space limitation during pregnancy, and would limit lambs’ coping abilities.