Maternal influences on milk intake in SHR and WKY pups.

Mother to pup milk transfer was examined in the spontaneously hypertensive rat (SHR) and its normotensive progenitor, the Wistar-Kyoto (WKY). Litters of SHR and WKY pups were either reared by their natural mothers or cross-fostered to mothers of the opposite strain shortly after birth. At postpartum days 7 and 14, pup body weights were monitored throughout a 2-h maternal separation period followed by a 3-h refeeding period during which pups remained with their mothers. Weight increases of pups over the refeeding period served as an indirect measure of milk ingestion. At postpartum day 7, both SHR and WKY pups nursed by SHR mothers received lower quantities of milk compared to their counterparts nursed by WKY mothers. Maternal strain differences in milk transfer were largely attenuated at postpartum day 14. The different nutritional environments provided by SHR and WKY mothers may mediate the alterations in offspring cardiovascular physiology and physical development that occur with reciprocal cross-fostering.