Doppler sonography of the uterine arteries during a superovulatory regime in cattle: Uterine blood flow in superovulated cattle

Transrectal color Doppler sonography was used to investigate the effects of a gonadotropin treatment to induce superovulation on uterine blood flow and its relationship with steroid hormone levels, ovarian response and embryo yield in dairy cows. The estrous cycle of 42 cows was synchronized by using PGF2α during diestrus and GnRH 48 h later (Day 0). Cows were examined on the day of eCG (2750 IU)-administration (Day 10), 3 days after eCG (Day 13) and 7 days after artificial insemination (Day 22), including the determination of total estrogens (E) and progesterone (P4) in peripheral plasma. Eight days after insemination (Day 23) the uterus was flushed and the number of total ova and embryos as well as transferable embryos was determined. The ovarian response was defined by the number of follicles > 5.0 mm in diameter on Day 13 and the number of corpora lutea on Day 22. Uterine blood flow was reflected by the blood flow volume (BFV) and the pulsatility index (PI) in the uterine arteries. Both variables showed distinct changes throughout the superovulatory cycle: BFV increased by 94% and PI decreased by 30% between Days 10 and 22 (P < 0.0001). On Day 13, BFV but not PI correlated with follicle numbers (r = 0.35; P < 0.05); no correlation was found with E and P4 (P > 0.05). On Day 22, BFV correlated positively and PI correlated negatively with the number of corpora lutea (r = 0.45 and r = -0.37; P < 0.05) and P4 (r = 0.39 and r = -0.30; P < 0.05). The number of transferable embryos was solely related to BFV measured on Day 13 (r = 0.32; P < 0.05). Our results show for the first time that in cows a superovulatory treatment is associated with a marked increase in BFV and a marked decrease in PI in the uterine arteries, concurrent with the development of multiple follicles and corpora lutea. However, transrectal color Doppler sonography of the uterine arteries does not facilitate the prediction of embryo yields following superovulatory treatment.