Blood flow changes in the duck during thermal panting

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Abstract
Carotid and sciatic blood flow were measured in resting and panting Pekin ducks using electromagnetic flowmeters. Panting induced by high ambient temperature caused carotid blood flow to increase from 9.6 to 26.0 ml/min while sciatic flow declined from 41.6 to 38.1 ml/min. During panting breathing rate increased 10-20 times but there were no significant changes in heart rate and mean arterial blood pressure. Carotid peripheral resistance was reduced but sciatic resistance remained unchanged or increased slightly. Vascular beds perfused by sciatic (legs) and carotid (upper respiratory tract) arteries were both important for heat dissipation. When heat dissipation from naked legs became inefficient due to high ambient temperature, blood flow in the sciatic tended to decline. Panting was associated with a large increase in carotid flow.