| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 2393425 | Domestic Animal Endocrinology | 2016 | 5 Pages |
•Efficacy of a GnRH agonist for synchronizing ovulation and follicular emergence in the “Day 0” superovulation protocol in Santa Inês ewes was assessed.•After progestogen sponge removal, ewes were treated with either saline (Gc) at 12 h, GnRH agonist at 24 h (G24h), or GnRH agonists at 36 h (G36h).•Ewes from G24h and G36h had earlier ovulation when compared with Gc.•G36h promoted the absence of dominant follicles during the first several days of estrus cycle.•It is suggested to start the superovulatory treatment at 80 h when applying G36h.
The ability of gonadotropin-releasing hormone (GnRH) to synchronize ovulation and new follicular wave emergence before a “superovulatory Day 0” protocol was assessed in Santa Inês ewes. For estrus synchronization, a 60-mg medroxyprogesterone acetate sponge was inserted for 6 d. One day before sponge removal, 37.5-μg d-cloprostenol and 300 IU equine chorionic gonadotropin were injected intramuscularly (i.m.). After sponge removal, ewes were assigned to the following 3 groups: (1) GC—1 mL saline at 12 h (n = 10); (2) G24h—0.025-mg lecirelin (GnRH agonist) i.m. at 24 h (n = 10); or (3) G36h—0.025-mg lecirelin i.m. at 36 h (n = 9). Ovarian ultrasonography was conducted to assess follicular dynamics. Blood was collected to determine plasma concentrations of progesterone and estradiol. Females from G36h and GC had a greater (P < 0.05) estrous response than those from the G24h group (78.0 and 90.0 vs 0.0%, respectively). Ewes from G24h and G36h had earlier (P < 0.05) ovulation (48.0 ± 10.2 and 56.7 ± 5.7 h) compared with those from Gc (64.1 ± 9.7 h). The mean number of ovulations per ewe was greater (P < 0.05) in Gc (1.9 ± 0.6) and G36h (2.0 ± 1.0) than G24h (1.2 ± 0.4). Plasma concentrations of progesterone and estradiol differed over time. Follicular growth during the postovulatory day was affected (P < 0.05) by day of the estrus cycle as well as by the interaction (P < 0.05) of treatment and day of the estrus cycle. There was a larger (P < 0.05) population of medium follicles during the first 24 h after the ovulation in G24h compared with Gc, and there was an absence of large follicles in G36h between 36 and 72 h after ovulation. In conclusion, the use of GnRH agonist at 36 h more efficiently synchronized ovulation and promoted the absence of dominant follicles during early diestrus and may be used at the start of superovulatory treatment at 80 h in Santa Inês ewes.
