A Simple Superovulation Method of A Single Injection of Follicle- Stimulating Hormone Combined with Equine Chorionic Gonadotropin for Superovulation of Suffolk Ewes During the Breeding Season: I. Effects of Different Treatments on the Endocrine Profiles

Abstract

Two trials were conducted to investigate a simple superovulation method for Suffolk ewes during the breeding season. The method involves a single injection of porcine follicle-stimulating hormone (pFSH) combined with equine chorionic gonadotropin (eCG) and was evaluated by measuring the concentrations of plasma hormones (estradiol-17β(E₂), progesterone (P₄), luteinizing hormone (LH) and follicle-stimulating hormone (FSH)). The ewes were treated with a vaginal sponge containing synthetic steroid with progestative action (P sponge) for 12 days in both trials. In Trial 1 (conducted in 1995), 18 ewes received a single injection (F1) or multiple injections (F6) of a total of 20 mg pFSH, and in combination with an injection of 500 IU eCG (F1+P, F6+P). The injections were conducted on Day -2 (Day 0 was the day of P sponge removal). In trial 2 (conducted in 1996), 24 ewes were given single injections of pFSH and eCG at different times; (i) both hormones on Day -2 (F-2/P-2), (ii) pFSH on Day -2 and eCG on Day -1 (F-2/P-1), and (iii) both hormones on Day -1 (F-1/P-1). One hundred micrograms of an analogue of gonadotropin-releasing hormone (GnRH) was administered on Day 1 in Trial 1 and at the detection of estrus in Trial 2. Frozen-thawed semen was inseminated in utero using a laparoscope at 30 h and 38 h after P sponge removal in Trial 1 and at 18 hours after the detection of estrus in Trial 2. Blood samples were collected from the jugular vein. E₂, P₄, LH and FSH were assayed by second-antibody enzyme immunoassays. F1+P showed similar endocrine profiles to those of F6 and F6+P with a preovulatory E₂ peak after P sponge removal, but F1 did not show a clear preovulatory E₂ peak. The E₂ concentration in F-2/P-1 rose biphasically; there was a rise just after injection of pFSH and then another rise after P sponge removal. Simultaneous injections of 20 mg pFSH and 500 IU eCG may reduce the E₂ elevation. We concluded that a good ovarian response comparable to the multiple injection method can be achieved by the present simple superovulation method.