Ovarian Responses, Hormonal Profiles and Embryo Yields in Anoestrous Ewes Superovulated with Folltropin®‐V after Pretreatment with Medroxyprogesterone Acetate‐releasing Vaginal Sponges and a Single Dose of Oestradiol‐17β

Abstract

In ruminants, superovulatory treatments started at the time of follicular wave emergence result in greater and less variable ovulatory responses and embryo yields compared with the treatments begun in the presence of a large growing antral follicle(s) from the previous waves. The progesterone-oestradiol treatment is routinely used for follicular wave synchronization in cattle. The main objective of this study was to characterize the ovarian responses, hormonal profiles and in vivo embryo production in anoestrous Rideau Arcott ewes (May-June), which were superovulated after pretreatment with medroxyprogesterone acetate (MAP)-releasing intravaginal sponges and a single dose of oestradiol-17beta (E(2)-17beta). Six days after insertion of MAP sponges, eight ewes were given an i.m. injection of 350 microg of E(2)-17beta (E(2)-17beta-treated ewes); 10 ewes were given an i.m. injection of vehicle (control ewes). Multiple-dose Folltropin-V treatment, followed by the bolus injection of GnRH (50 microg i.m.), began 6 days after E(2)-17beta/vehicle injection. Transrectal ovarian ultrasonography revealed that: (i) the interval between E(2)-17beta/vehicle injection and regression of all follicles > or =5 to 3 mm in diameter was shorter (p < 0.01; 2.6 +/- 0.4 vs 4.8 +/- 0.6 days respectively); and (ii) the interval between injection and emergence of the next follicular wave was longer (p < 0.05; 5.4 +/- 0.3 vs 1.2 +/- 0.4 days, respectively) in E(2)-17beta-treated than in control ewes. During the 6 days after injection, the mean FSH peak concentration and basal FSH concentration were lower (p < 0.01) in E(2)-17beta-treated ewes. The mean ovulation rate and the number of recovered embryos did not differ (p > 0.05) between the two groups of ewes. However, the number of luteinized unovulated follicles per ewe, and the variability in the number of luteal structures and overall embryo yield were less (p < 0.05) in E(2)-17beta-treated compared with control ewes. In conclusion, the MAP-E(2)-17beta pretreatment significantly reduced the variability in ovarian responses and embryo yields, without affecting the embryo production in superovulated anoestrous ewes.

Systemic Concentrations of Endogenous and Exogenous FSH in Anoestrous Ewes Superstimulated with Folltropin®‐V

“…The superovulatory treatment with Folltropin ® ‐V initiated 6 days after E 2 ‐17β injection was associated with the reduced variability in ovulation rates and embryo yields. Although the treatment with MAP and E 2 ‐17β increased the number of ovulatory‐sized antral follicles growing in response to Folltropin ® ‐V, there has been no increase in the ovulation rate in the treated anoestrous ewes (Bartlewski et al. 2008b).…”

“…The synchronization of follicular wave emergence with the progestin/oestradiol‐17β (E 2 ‐17β) treatment prior to ovarian superstimulation in seasonally anoestrous ewes reduced the variability in superovulatory responses without compromising embryo yields (Bartlewski et al. 2008b).…”

“…The administration of a single dose of 350 μg of E 2 ‐17β to medroxyprogesterone acetate (MAP)‐treated ewes suppressed follicular wave emergence for 4–6 days (Barrett et al. 2007; Bartlewski et al. 2008b).…”

“…The suppression of antral follicular growth by the MAP/E 2 ‐17β treatment appeared to be due mainly to partial suppression of follicle‐stimulating hormone (FSH) release (Barrett et al. 2007; Bartlewski et al. 2008b).…”

Recent Advances in Reproductive Biotechnologies in Sheep and Goat

“…This breeding model has been extensively used to multiply genetically superior goats and sheep and many protocols have been developed to optimize its application in research as well as in commercial practice [22][23][24][25]. In most domestic farm animals, especially in cattle, the genetic gain is limited on the female side due to low reproductive rate with only one calf being produced per year and also relatively long intervals between generations.…”