195 Are the Spectral Doppler Indices of the Ovarian Arteries Predictive of Ovulatory Responses and Embryo Yields in Superovulated Ewes?

Abstract

Increased uterine and ovarian blood flow seems to be related to the effectiveness of ovarian response to hormonal superstimulation in mares (Witt et al. 2012 Theriogenology 77, 1406-1414). Similar studies do not exist for sheep. Nineteen Santa Inês ewes were subjected to a 9-day CIDR® priming and superovulatory (SOV) treatment with 200 mg of porcine (p)FSH per ewe given twice daily for 4 consecutive days in decreasing doses and initiated 6 days after CIDR® insertion. Ten ewes received an IM injection of oestradiol benzoate (EB, 350 μg) at the time of CIDR® insertion (group E); the remaining animals served as controls (group C). The ewes were placed in a pen with rams for 3 days after CIDR® removal. The embryos were recovered surgically 6 days after the CIDR® removal. Transrectal ultrasonographic examinations (Doppler mode) using MyLab VET 30 scanner (Esaote, Genoa, Italy) equipped with a linear-array (6- to 8-MHz) transducer were performed once a day throughout the SOV treatment (Days 1 to 4) to determine the velocimetric indices of the left and right ovarian arteries: flow velocity integral (FVI); peak systolic velocity (SVp); mean velocity (Vm); end-diastolic velocity (EDV); vascular resistance index [RI = (SVp – EDV)/SVp]; and pulsatility index [PI = (SVp – EDV)/Vm]. All spectral data were obtained from a longitudinal subovarian segment of the ovarian artery using a gate ranging from 2 to 3 mm (~two-thirds of the vessel’s diameter) and insonation angle ≤60°. There were no differences (P > 0.05) in ovarian responses and embryo yields/quality between left and right ovaries/uterine horns flashed or between EB-treated and control ewes. Mean EDV and Vm were greater (P < 0.05) in group C compared with group E on Days 1 and 2, and mean Vp was greater (P < 0.05) in group C ewes on Day 3 of the SOV treatment. In group E, there were 5 significant correlations between the spectral Doppler indices (RI, PI, and EDV) of the ovarian arteries recorded on Days 2 and 4 and SOV responses (numbers of degenerated embryos, unfertilized eggs, and luteinized unovulated follicles characterised by a lack of ovulatory stigmata). In group C, 7 significant correlations were found between Vp, EDV, Vm, and RI on Days 1, 2, and 3 and numbers/percentages of degenerated embryos, numbers of prematurely regressed luteal structures (pale, ≤5 mm in diameter), and embryo viability rates (percentage of transferrable quality embryos). When ultrasonographic and SOV data were analysed separately for the left and right ovarian artery/uterine horn, multiple significant correlations were found between the velocimetric indices and SOV responses but they varied among days, the 2 ovaries, and the 2 groups of animals studied. These results may be interpreted to suggest that intrinsic gonadal factors remain a significant barrier precluding the prediction of SOV outcomes from haemodynamic changes in ovine ovarian arteries. Velocimetric indices determined in the ovarian arteries appear to have limited prognostic value during the application of different SOV protocols in ewes.