Psychobiological consequences of two different weaning methods in sheep.

Weaning is associated with a break in the mother-infant contact. In sheep, under natural conditions, the rupture of the social bond is progressive. In contrast, weaning imposed by breeders may result in psychobiological disturbances. The aim of this experiment was to measure the behavioural, hormonal and immune consequences of two types of sudden weaning: total separation (TS) and partial separation (PS), in 42 Ile-de-France ewes and their 60 lambs. TS animals (lambs and ewes) vocalized less frequently and for a shorter period of time than did the PS animals. Neither the plasmatic cortisol level in lambs nor the humoral response of dams and young were modified by the two weaning methods. In contrast, the excretion of coccidial oocysts increased significantly after weaning in TS lambs only and the growth rate of TS females was lower than that of the other lambs. These results suggest that these methods of rupture of mother-young social contact have only limited negative consequences on both partners in sheep, contrary to primates and rodents.