The synchronization of nursing bouts in group-housed sows

Abstract The synchronization of nursing bouts was quantified in three groups of four sows under conditions of group housing when the litters were between 2 and 8 weeks old. In 82.3% of all observed nursing bouts there was a temporal overlap in the nursing bouts of two or more sows. The mean duration (± SD) of the interval between the time when the first and the last sow participating in a group nursing bout reached a state in which half of the litter was massaging the udder white the sow was grunting was 1.2 ± 1.3 min ( N = 502 group nursing bouts). A total of 1509 transitions from an ongoing nursing bout to the start of a new, temporally overlapping nursing bout in another sow and her litter were analysed. In 93.0% of these transitions the start of the new nursing bout was preceded by particular acoustic behaviour patterns from the sow or the piglets in the ongoing nursing bout. The piglets were more often observed to perform the first behaviour pattern in a synchronized nursing bout than the sows, and the piglet's importance for the synchronization increased with age. In an experimental part of the study, one of the groups was confronted with playbacks of nursing grunts. It could be shown that nursing grunts are effective in eliciting nursing bouts. There were indications that the synchronization of nursing bouts in domestic pigs may be based on social facilitation, as well as on learning mechanisms.