PREPARTURIENT VARIATION IN PROGESTERONE, PROLACTIN, OXYTOCIN AND SOMATOSTATIN IN RELATION TO NEST-BUILDING IN SOWS

Progesterone, prolactin, oxytocin and somatostatin concentrations in the plasma of ten multiparous Swedish Landrace sows were measured during the last 72 h prepartum and related to nest-building behaviour. The beginning of nest building was determined when the sow started to take straw from the rack and to deposit it. Rooting, pawing and arranging straw, and taking and carrying straw were recorded as separate behaviour components. Nest building started within 24 h and peaked 6-12 h before parturition. Only prolactin concentrations 2 days before parturition were independently correlated with the nest-building onset. Prolactin levels started to increase before the nest-building onset and only reached maximum values after it, suggesting that it is the preparturient rise in prolactin concentration that initiates nest building. The duration of carrying and depositing straw correlated positively with progesterone concentrations and negatively with somatostatin concentrations 2 days before parturition. Nest building ceased within 4 h before parturition. Oxytocin concentration 8 h before parturition was related to the end of nest building. The results suggest that nest building in sows is under multiple hormonal control and that the beginning and end, and the different behaviour types are related to different parturient endocrine changes.