Diversity in sheep affiliative relationships under farming conditions: behavioural and neurobiological mechanisms

Abstract

The sheep is well known to develop various forms of social attachment. The onset of maternal responsiveness and the development of the mutual mother-young bond are under the combined influence of hormonal and peripheral somatosensory stimulations. These stimuli are provided by parturition in the mother and by the first suckling episodes in the neonate. Following parturition, the main olfactory bulbs of the ewe undergo profound neurophysiological changes when exposed to offspring odours while activations in the hypothalamus contribute to maternal responsiveness and memorization of lamb odours. Similarly, in the neonate the hypothalamus and the amygdala respond to colostrum ingestion. Oxytocin, a neuropeptide known to play a key role in prosocial behaviours, facilitates mother-young bonding. When new-born lambs are separated from their mother to be artificially-fed, a very common farm practice, they are profoundly affected. Neuroendocrine responses suggest that lambs are in a situation of distress. However, should a human caregiver look after them, an interspecific bond is then facilitated by positive social contacts including bottle-feeding or stroking. These contacts activate the oxytocinergic system, like in the mother-young bonding process. Thus, under artificial rearing conditions,the human becomes a salient attachment figure who may facilitate the management of lambs on farms.