Postprandial gastrointestinal blood flow, oxygen consumption and heart rate in rainbow trout (Oncorhynchus mykiss)

The present study is the first to simultaneously and continuously measure oxygen consumption (MO2) and gastrointestinal blood flow (qgi) in fish. In addition, while it is the first to compare the effects of three isoenergetic diets on qgi in fish, no significant differences among diets were found for postprandial MO2, qgi or heart rate (fH) in rainbow trout, Oncorhynchus mykiss. Postprandial qgi, fH and MO2 were significantly elevated above baseline levels by 4 h. Postprandial qgi peaked at 136% above baseline after 11 h, fH peaked at 110% above baseline after 14 h and MO2 peaked at 96% above baseline after 27 h. Moreover, postprandial MO2 remained significantly elevated above baseline longer than qgi (for 41 h and 30 h, respectively), perhaps because most of the increase in MO2 associated with feeding is due to protein handling, a process that continues following the absorption of nutrients which is thought to be the primary reason for the elevation of qgi. In addition to the positive relationships found between postprandial MO2 and qgi and between postprandial MO2 and fH, we discovered a novel relationship between postprandial qgi and fH.