Sensory Factors Involved in Immediately Postnatal Ewe/Lamb Bonding

Abstract

Abstract1. Aspects of the ewe which influence the lamb. Lambs were removed from their mothers at birth and tested under one of seven conditions : (1) with the dam in her pen, or, in a circular arena, (2) in the presence of a stationary model ewe, (3) with the same model, but moving, (4) in the presence of a large, headless and legless moving object, (5) with stimulation by the sound of recorded bleats, (6) with tactile stimulation or (7) with no stimulation. Indices of responsiveness included movements of righting and standing, approach to the model, bleating and nosing of the model or the arena. Results showed that lambs tested with the stationary model stood most slowly whereas the presence of the moving model ewe was associated with rapid standing. The groups with no experimental stimulation at all, or with stimulation by the sound of recorded bleats, also stood rapidly. Bleating of the lambs was most prevalent in the group with no stimulation at all. Lambs presented with moving models approached them more rapidly and nosed them more than did those tested with the stationary model. More than any others, lambs in the "stationary model" group were quiescent for long periods. Lambs tested in the presence of their mothers and those given tactile stimulation were consistently low in the rank order for all indices of response; in particular they stood more slowly and bleated less than groups presented with moving models. It is concluded that the dam is a composite stimulus for her lamb; she activates it when she moves but also elicits responses which reduce its early activity. 2. Aspects of the lamb which attract the ewe. Ninety Merino ewes, from each of which the lamb had been removed at birth, were tested in their own pens under one of the following conditions: (i) with their own lambs; (ii) with a warm, moving lamb model soaked in amniotic fluid and accompanied by lamb bleats, or with the same model but (iii) without movement; (iv) without warmth; (v) without bleats or (vi) without amniotic fluid. A seventh group was tested with a white bowl of warm amniotic fluid, also moving and accompanied by lamb bleats. The ewes approached their own lambs and were much more attentive to them, than to any of the models. The model which received the least attention was that (vi) with no amniotic fluid, while the 'model' which received the most was (vii) the white bowl containing amniotic fluid.