We evaluated 17 healthy neonatal piglets to determine the effects of an increased hyperosmolal formula (HOF; 874 +/- 30 mOsmol/kg, n = 9) and commercial pig milk formula (CF; 482 +/- 35 mOsmol/kg, n = 8) on small intestinal myoelectric activity (SIMEA). Four bipolar electrodes were surgically implanted along the small intestine to evaluate myoelectrical parameters and patterns of SIMEA during fasting and postprandial periods. Durations of myoelectric phase activity and migrating motility complex periodicity were unaffected by both formulas. Differences in SIMEA were not significant when CF and HOF were compared. Following a single meal of increased HOF, piglets demonstrated a significant postprandial increase of phase 2 myoelectric activity in the duodenum through ileum (p less than 0.05) and time-dependent decrease of phase 3 activity in the duodenum (p less than 0.05) and jejunum through terminal ileum (p less than 0.01). Diminished phase 3 activity in the terminal ileum persisted throughout the 4-h postprandial period (p less than 0.01) and was related to fewer phase 3 episodes in this region (p less than 0.05). This pattern of myoelectric activity has been associated with decreased intestinal propulsion and clearing of intraluminal contents. We conclude that a single meal of HOF does not result in significant intestinal motor dysfunction in healthy neonatal piglets. It remains to be determined whether postprandial reductions of phase 3 myoelectric activity that follow a hyperosmolal meal serve as a precursor to neonatal necrotizing enterocolitis when additional risk factors exist.