Recognition of the sow's voice by neonatal piglets

Piglets were tested for recognition of their sow's voice at 1, 2 & 6 days of age. Each piglet was tested individually by playing one minute of recorded grunts from its own sow and one minute of recordings from an alien sow, compared with a one minute period alone with no sound. The vocalizations of the piglets were recorded and analysed. Some piglets responded to their own sow's voice by making rapid 'quacking' grunts which differed in tone from the 'closed mouth grunts' made alone; some piglets responded by orientation and movements towards the sound. At one day old 29% piglets responded vocally exclusively to their own sow and 52 % responded when movement was included as a sign of recognition. 27 % piglets responded to both own and alien sow voices. At 2 days the response had become exclusive to their own sow's voice and 87 % piglets responded (57 % vocally). At 6 days 81 % piglets responded positively to their own sow's voice (62% vocally). The number of grunts increased in each minute of the tests with 1 and 2 day old piglets regardless of treatment, but at 6 days old, the piglets grunted more to their own sow's voice than to an alien.