Effect of Lying Behavior on Uterine Blood Flow in Cows During the Third Trimester of Gestation

Abstract

Seven Holstein cows (BW = 639.4±28.8kg, age = 62.6±6.9 mo, parity = 3.1±0.4 yr) (mean±SE) were used to measure uterine blood flow using a transit time ultrasonic flow meter. Ultrasonic flow probes were implanted (d 218±4 of gestation) around both uterine arteries (n = 3) or the gravid uterine artery (n = 4) to measure variations in uterine blood flow through this vessel in response to postural change (standing and lying). Implantation of the ultrasonic blood flow probe was successful in all 7 cows. Uterine blood flow was measured for 22.9, 23.1, and 21.4 h/d on d 226, 248, and 269 of gestation, respectively. Cows exhibited normal durations of gestation (272.8±1.6 d), gave birth to normal healthy calves (birth weight = 41.5±3.0kg), and did not retain their placenta. Uterine blood flow to the gravid horn during lying was greater than during standing on d 226 (standing vs. lying, 8.04 vs. 8.79 L/min, respectively), d 248 (9.87 vs. 11.06 L/min), and d 269 (8.15 vs. 9.74 L/min) of gestation. Cows spent nearly 50% of their time lying during our observations at all gestational ages. Greater blood supply to the gravid uterus was observed during lying than during standing in this study.