Decrease of response to social separation in preparturient ewes

The response to social isolation was compared in multiparous non-pregnant (controls) and periparturient (experimental) Rambouillet ewes over three tests performed at times corresponding to 111+/-31 h prepartum (148 days of pregnancy), 3.1+/-1.2 h prepartum (after onset of labour) and 1.3+/-0.2 h postpartum for the experimental group. Twenty-four and 15 ewes (test 1), 16 and 12 (test 2) and 7 and 10 (test 3) were tested in control and experimental groups respectively. Each test lasted 10 min (5 min in presence of conspecifics, 5 min in their absence). High-pitched bleats, locomotor activity, attempts at jumping out of the testing pen, eliminations and latency out of the pen were recorded. In both groups and in all tests there was a significant increase of agitation following removal of the conspecifics. Few differences were encountered between groups in the first test. On the other hand, in the second and third tests the agitation induced by social separation was significantly higher in dry ewes for the great majority of behaviours. We conclude that the reduction of response to social separation previously reported in postparturient ewes is not totally due to the maternal bonding to the neonate, but that before parturition, some physiological factors internal to the mother already reduce gregariousness. (C) 1997 Elsevier Science B.V.