The influence of temperature variation upon vascular dynamics in cattle as measured by Doppler-image ultrasonography

Two studies were performed to determine if Doppler ultrasound can detect vascular changes in cattle exposed to hot and cold conditions. Three calves per study (320±38 kg) were acclimated to 17.5oC, and then exposed to 32oC and 8oC. Animals were maintained under these conditions for 24 h and then returned to the original thermoneutral level. Three replicated ultrasound measurements of the median caudal artery were performed. Scans were repeated at -2, 5, 23, 24 and 28 h. Blood flow rates of 32oC cattle ranged from 27.84 (-2 h) to 43.42 ml/min at 23 h (P