Transrectal Doppler sonography of uterine blood flow in cows during the estrous cycle

Transrectal Doppler ultrasound was used for the noninvasive investigation o f uterine blood flow in cows. Both the left and right Aa. uterinae were sca nned to obtain blood flow velocity waveforms over 2 consecutive estrous cyc les. Blood flow was reflected by the resistance index (RI) and the time-ave raged maximum velocity (TAMV). Intra-observer reproducibility of Doppler me asurements was evaluated. The intra-class correlation coefficient (Intra-CC ) was 0.97 for the RT and 0.95 for TAMV. While RI values did not differ bet ween the left and right A. uterina (P > 0.05), differences in TAMV occurred between both vessels in 2 cows. These differences were not related to the ovary bearing the dominant follicle or to the corpus luteum (P < 0.001). As in all cows, changes of RI and TAMV values between the left and right arte ry during the estrous cycle were correlated (correlation coefficient r > 0. 72; P < 0.0001); the mean values of both sides were used for subsequent ana lyses. Variance component estimates for the effect of cow on RI and TAMV we re 8 and 13% and for the influence of day of estrous cycle they were 70 and 47%, respectively (P < 0.0001). Between estrous cycles no significant diff erences could be measured within cows (P > 0.05). The highest RI and lowest TAMV values occurred on Day 0 (= day of ovulation) and Day 1, while the lo west RI and highest TAMV values were measured between Days -3 and -1 of the estrous cycle, respectively. There was a positive correlation between TAMV and estrogen concentrations and a negative correlation between RI and plas ma estrogen levels. Plasma progesterone levels and TAMV were negatively cor related, but no correlation could be measured (P > 0.05) between RI values and plasma progesterone concentrations. While there were no differences in plasma concentrations of estrogens and progesterone between estrous cycles within cows, the levels of these hormones differed between cows. The result s show that transrectal Doppler sonography is a useful, noninvasive method for examining uterine blood flows in cows. If there is an influence of uter ine perfusion on fertility in cows its role needs further investigation. (C ) 2000 by Elsevier Science Inc.