Blood flow distribution during graded treadmill exercise in domestic cockerels.

1. White Leghorn cockerels were exercised continuously for 45 minutes on a treadmill at work loads equivalent to 2.1 and 2.7 times pre-exercise metabolic rates, the latter being close to the performance limits of the experimental birds. 2. Relative blood flow to the abdominal viscera and selected leg muscles was estimated using 113Sn-, 153Gd- and 46Sc-labelled microspheres, injected into the root of the aorta. 3. There was no significant shift of blood flow away from the viscera towards the leg muscles at either work load. However, relative colonic and duodenal blood flow fell significantly at both work loads and relative pancreatic blood flow doubled at the higher work load. 4. It is concluded that, as previously reported in female domestic fowl performing physical exercise close to their performance limits, male fowl are largely refractory to shifts in blood flow away from the viscera to the working muscles. Nevertheless, there is evidence of blood flow shifts between visceral organs, probably related to the intermediary metabolism of fuel substrates.