Synchronization of follicular wave emergence does not improve embryonic yield in superovulated ewes

Abstract

The present study aimed to investigate the effects of a combination of progesterone with different doses of E-17β on following end points: (1) ovarian follicular dynamics and emergence of a new follicular wave, and (2) superovulatory response and embryo yield. In Experiment 1, 28 ewes were randomly divided into four groups (n = 7) to receive either 2.0 mg, 1.0 mg, 0.5 mg or none E-17β one day after insertion of a progesterone device. The different doses of estradiol similarly delayed the moment of follicular emergence (overall mean = 3.1 ± 1.0 days vs. control group = 0.86 ± 1.0 days; P < 0.01), but the emergence of the new wave showed greater synchronization with the 0.5 mg dosage of E-17β. In Experiment 2, sixtytwo donor ewes received an internal progesterone release device (day -1) for 7 d and 1 d after the insertion of this device (day 0) were allocated randomly to receive 0.5 mg of E-17β or only the vehicle (control group). Superstimulation was initiated on day 3 with the administration of 133 mg of pFSH in eight decreasing doses. Contrary to expectations, the protocol with the administration of 0.5 mg E-17β did not improve the percentage of donors with > 2 CL, the number of CL and the production of embryos (P > 0.05). It was concluded that the combination of progesterone and 0.5 mg E-17β was more efficient in synchronizing the emergence of the new follicular wave, however this approach seems to be unnecessary in ewe's superovulation programs.

Ovarian assessment for pre-selection of embryo donor ewes

“…The number of small follicles assessed at the first administration of FSH has been positively correlated with the ovulation rate and the number of viable embryos in many studies (Gonzalez-Bulnes et al, 2000Mossa et al, 2007). However, other authors have not verified this correlation (Bruno-Galarraga et al, 2014;Brasil et al, 2021). In this study, the superovulatory response and embryo production were positively correlated with the number of follicles ≥ 2 mm in metestrus.…”

“…Therefore, it seems that the evaluation of the number of follicles ≥ 2 mm has a greater correlation with the superovulatory and embryo yield parameters when performed closer to the emergence of the follicular wave. A possible alternative to quantify follicles ≥ 2 mm at a more predictable time of follicular wave emergence would be the use of the progesterone protocol associated with the application of 0.5 mg of 17β-estradiol (17β-E), which allows the recruitment of the synchronized form wave 2.8 days after 17β-E administration (Brasil et al, 2021).…”

The Role of Certain Specific Hormonal Treatments in Estrus Synchronization of Ewes: A mini Review

“…Treatment with progesterone for a period of 18 -21 days resulted in low fertility rates, and this has been attributed to the ovulation of permanent follicles containing ova of inferior quality. The decrease in fertility can also be attributed to the adverse effects of progesterone within the internal uterine environment that affect sperm transfer and life [52].…”