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: II. The Ovarian Responses and the Embryo Qualities

Two trials were conducted to investigate the effects of a simple superovulation method using a single injection of porcine follicle-stimulating hormone (pFSH) combined with equine chorionic gonadotropin (eCG) on ovarian responses and embryo qualities in Suffolk ewes during the breeding season. The ewes were treated with a vaginal sponge containing synthetic progestative steroid (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 h after the detection of estrus in Trial 2. Embryos were recovered on Day 7 or Day 8. In Trial 1, the mean number of ovulations and the rate of normal embryos were 6.8, 16.7% for F1, 15.0, 36.0% for F1+P, 15.5, 27.0% for F6 and 20.3, 44.2% for F6+P. The F1+P group showed the results comparable to those of F6 and F6+P. In Trial 2, the mean number of ovulations were 17.8 for F-2/P-1, 13.1 for F-2/P-2 and 12.4 for F-1/P-1. The rate of normal embryos in F-2/P-1 (63.0%) was significantly higher than in F-2/P-2 (41.1%, P