Nursing interaction of Wistar rats is modified by prior experience of altered nursing bout length

We tested the capacity of 2 week postpartum Wistar rat litters and their dams to adapt to experimental shortening and lengthening of the time available for nursing while maintaining the frequency of bouts constant, using manual transfer between cage compartments. In 8-hr and 24-hr experiments, the short bout group (10 min/hr) gradually came to show normal litter weight gain, short latency milk ejections, and increased high arched nursing position, while the 40-min/hr group showed increased latency to attachment and longer latency to ME compared to the 20 min/hr control group. Pup body temperature did not vary between groups. Although pups in the 10-min group showed increased dam-directed behaviors in the first 8h, this difference vanished thereafter. In a twenty-fifth cycle, after dams and litters were exchanged, the prior experiences of the dams and not of the litters were found to determine the dynamics of milk exchange.