|Spiers, D - UNIVERSITY OF MISSOURI|
Submitted to: American Society of Animal Science Proceedings
Publication Type: Other
Publication Acceptance Date: April 11, 2006
Publication Date: July 10, 2006
Citation: Kirch, B.H., Aiken, G.E., Spiers, D. 2006. Temperature influences upon vascular dynamics as measured by doppler ultrasonography. American Society of Animal Science Proceedings. J. of ANim. Sci. 84:(Suppl 1) 212. Technical Abstract: Two preliminary studies were performed using doppler-image ultrasound to document the vascular changes of cattle under hot and cold conditions. Three calves per study (320 ± 38 kg) were acclimated to thermoneutrality in the Brody Environmental Center at the University of Missouri. A minimum of three ultrasound measurements were taken of the median caudal artery at the 4th coccygeal vertebrae (Cd4) using a 13 mhz probe. The animals were then stressed by either raising air temperature to 32oC or reducing it to 8oC. The animals were housed under these conditions for 24 h and then returned to thermoneutral temperatures. Ultrasound scans were repeated at -2 (2 h prior to temperature change), 5, 23, 24 and 28 h (4 h after returning to thermoneutrality) after being put under climatic changes. Blood flow rates of heat stressed cattle significantly increased from 39.12 (-2 h) to 59.87 mm/min at 23 h of exposure (P < 0.05). The vessel diameter tended to increase (0.047 to 0.063 cm2) with the onset of the stress but was not statistically significant. Heart rate (82 beats/min) was unchanged throughout the study, but respiration rate did increase from 82 (-2 h) to 120 breaths/min (23 h). Cattle placed under cold stress showed lower flow rates to the caudal artery after 23 h of exposure (P < 0.10) (30.73 at -2 h to 18.44 mm/min at 23 h). Blood flow rates of the cold stressed cattle initially increased after the challenge. At 5 h post temperature reduction, flow rates were 53.9 mm/min, increasing over the baseline of 30.7 mm/min (P < 0.07). Under cold conditions heart rate was unchanged and averaged 79 beats/min across all five time periods while respiration rate decreased from 62 (-2) to 36 breaths/min (23 h). Arterial area increased from 0.057 to 0.072 cm2 at 5 h (P < 0.07) then decreased to 0.043 mm2 at 23 h. The doppler-image ultrasound detected vascular changes due to environmental variation and lends itself to future studies assessing environmental stress effects on hemodynamics.