Our aim was to characterize the postprandial total and dietary N fluxes in the portal drained- viscera (PDV) and whole-body after administration of a single meal in young pigs. Seven 4-wk old piglets, implanted with a portal flow probe and portal, arterial and venous catheters, received a primed constant ¹⁸O-urea i.v. infusion and were studied for 8h after a bolus mixed meal ingestion (46 mmolN/kgBW) intrinsically labeled with ¹⁵N to trace dietary N fluxes. The real cecal digestibility of the formula was 94.3±1.8%. PDV output of dietary N was principally found in the pool of circulating protein (51% of the measured dietary N PDV output), in the free -amino N pool (44%), and to a lesser extent in ammonia (5%). Dietary N release in -amino N and ammonia mainly occurred during the first 3h. Total and exogenous postprandial urea productions were 5.8 and 2.0 mmolN/kgBW, respectively. At the end of the postprandial period, losses of dietary N amounted to 10.3% of the dose: 5.7% through ileal losses and 4.6% by deamination and transfer to urea. The net postprandial retention of dietary N was 90.4±1.3%, out of which 20% was found in splanchnic zone (small intestine: 10%, liver: 5% and plasma protein: 3%) and 42% in peripheral zone (muscle: 31%, skin: 6%). In conclusion, our results show a high efficiency of dietary N utilization for muscular uptake and anabolic utilization. However, the results obtained point out the necessity to further explore the form of dietary N released into the portal blood.