Collateral uterine blood flow in Holstein cows during the third trimester of pregnancy

Blood flow to the gravid and nongravid uterine horns of four multiparous Holstein cows (mean +/- SD, BW=641.8 +/- 95.4 kg; age=4.8 +/- 1.2 years; parity=3.0 +/- 1.2) was measured on days 225, 248, and 266 of gestation. Surgery was conducted on day 214.5 +/- 4.0 of gestation through the flank of the standing cows. Transit-time ultrasonic flow probes (diameter 12 or 14 mm) were fitted surgically around the uterine arteries of each cow. Surgery was completed within two hours of anesthesia, and the animals recovered rapidly following surgery. Uterine blood flow (UBF, l/min) was recorded at 10 sec intervals for approximately 23.5 hours; these values were averaged to determine UBF. The mean gravid UBF was significantly (P<0.05) greater than the nongravid UBF in this study. The range of the gravid and nongravid UBFs varied from 3.61 to 14.05 and 0.72 to 6.54 l/min, respectively. There were no changes (P>0.1) in the mean gravid and nongravid UBFs from day 225 to 266 of gestation.