Potential role for GnRH in the synchronization of follicular emergence before the superovulatory Day 0 protocol

Whole issue

“…The percentage of goats ovulating of 93.10% (27/29), regardless of the application time of GnRH, showed the efficiency of the synchronization protocol used in this study (Table 1). Likewise, using the same protocols as in the present study Balaro et al (2016) reported no significant difference in the percentage of ovulating (96.5%) between Santa Inês ewes treated with GnRH (0.025 mg, lecirelin) 36 and 24 hours after removal of the sponges. Similarly, using 20 mg FGA sponge for 6 days with 300 IU eCG and 30 µg of d-cloprostenol, Cavalcanti et al (2012), reported 100 and 90 % the mean number of ovulations in ewes non-treated or treated GnRH (25 µg, licerelin) 24 h after sponge removal, respectively, during breeding season, and no significant difference between groups were also observed.…”

“…Additionally, GnRH injection 36 and 24 hours after sponge withdrawal did not change the concentration of P 4 and E 2 during and following ovulation. Similarly, Balaro et al (2016) applied GnRH injection at 36 and 24 hours after sponge removal reported that, in ewes, plasma concentrations of P 4 and E 2 could not find any difference. Anyway, a direct comparison of ovulation time and hormone concentration in nulliparous and multiparous goats between studies is difficult due to differences in breed, hormonal milieu, age, nutrition status and synchronization protocols.…”

“…Knowledge of the timing of ovulation would permit more precise timing of mating or artificial insemination (Freitas et al, 1997;Simões et al, 2008). More close synchronization of ovulation(s) could be achieved by supporting the preovulatory LH peak with exogenous hormones such as the gonadotropin releasing hormone (GnRH) or human chorionic gonadotropin (hCG), as in sheep (Balaro et al, 2016) and cows (Fonseca et al, 2001). Similarly, a single injection of GnRH 24 h after norgestomet implant removal has been used to induce ovulation of dominant follicle in Baladi goats during the non-breeding season (Medan et al, 2002).…”

Use of oxytocin to attain cervical dilation for transcervical embryo transfer in sheep

“…To simulate physiological dioestrous conditions at embryo transfer, ewes were previously submitted to an oestrous synchronization protocol according to Balaro et al. (2016). Briefly, a sponge impregnated with 60 mg of medroxyprogesterone acetate (Progespon ® , Schering Plough) was inserted for 6 days.…”

Towards Improving the Outcomes of Multiple Ovulation and Embryo Transfer in Sheep, with Particular Focus on Donor Superovulation

“…Therefore, combining a GnRH agonist at 36 h after sponge removal, as in the short-term protocol, with the start of superovulatory treatment at 80 h, may be recommended in ewes. The GnRH agonist at 24 h compared to 36 h after sponge removal showed no estrus response (0.0% vs. 78.0%) [ 65 ]. The GnRH at 36 h after sponge removal efficiently synchronizes ovulation in ewes treated with FSH due to the improved synchrony in ovulation, promoting the absence of the dominant follicles, which improves fertilization rate and increases the production of viable embryos [ 64 ].…”