Milk delivery schedules and stomach preloading after patterns of suckling behavior by newborn rats on a surrogate nipple

Newborn rat pups tested before suckling experience attached to and ingested milk from the surrogate nipple. Time attached to the nipple and amount of milk ingested depended on the schedule of milk infusion through the nipple. More frequent milk infusions resulted in more frequent disengagements from the nipple during the test, less time attached to the nipple, and less bod y weight gain. The initial patterns of attachment behavior-continuous or in termittent-were reproduced later when rats were tested on the surrogate nip ple. Preloading of the stomach with milk effectively altered both attachmen t and ingestion from the nipple, whereas preloading with the same amount of water had no effect on suckling behavior. The data suggest that newborn ra ts flexibly adjust their attachment behavior to peculiarities of milk deliv ery through the surrogate nipple and reproduce the initial attachment patte rn when reexposed to the surrogate nipple.