Regional and total gastrointestinal (GI) blood flow, O2 delivery, O2 extraction, and O2 consumption were measured before and after acute blood volume expansion in 2-day-old piglets. Blood flow was measured with radionuclide-labeled microspheres. Sixty minutes after a rapid transfusion of age- and hematocrit-matched piglet donor blood, 51Cr-measured blood volume increased 19% while an increase in hematocrit suggested plasma transudation to the extravascular space had occurred in response to blood volume loading. Following transfusion, total GI blood flow and O2 delivery did not change, although O2 extraction decreased by 31 +/- 4%. O2 consumption by the GI tract decreased from 2.0 +/- 0.19 ml O2 X min-1 X 100 g-1 to 1.46 +/- 0.24 ml O2 X min-1 X 100 g-1 1 h after transfusion. Feeding was then accomplished via orogastric tube to determine if animals stressed by blood volume loading would increase GI O2 consumption in response to feeding. The postprandial increase in GI O2 consumption was similar to that previously reported in newborn piglets. Therefore, in the fasting state, acute blood volume loading disrupts GI O2 transport at the capillary level and decreases GI O2 consumption. However, animals subjected to blood volume loading appear capable of increasing GI O2 consumption after feeding.