Comparative studies of four different intravaginal devices containing progesterone or synthetic progestogens on estrous incidence, LH surge and fertility of synchronized ewes by an intrauterine insemination with frozen semen by laparoscopy were conducted during the breeding season. A total of 161 Suffolk or Suffolk-crossed ewes at two sheep farms (Farms A and B) were used. In Farm A, the mean times of estrous onset after the removal of four intravaginal devices were 27.3, 31.2, 21.8 and 22.8 h for MAP, FGA, CIDR and P sponge (self-made progesterone sponge), respectively. The progesterone-impregnated intravaginal devices (CIDR and P sponge) induced estrus significantly earlier (P<0.05) than the devices impregnated with the synthetic progestogens (MAP and FGA) (22.3 ± 2.0 and 29.4 ± 2.3 h, respectively, after the removal of the intravaginal device). CIDR induced estrus (P<0.01) and LH surge (P<0.05) significantly earlier than FGA and MAP sponges, respectively. Pregnancy determined by the plasma progesterone concentration (>2.0 ng/ml) on Day 21 (Farm B) and lambing rates (Farms A and B) of ewes inseminated once on a fixed-time basis between 44 and 52 h after removal of intravaginal devices were not significantly different: 45.0, 41.5, 57.9 and 39.5% in lambing rates for MAP, FGA, CIDR and P sponge, respectively. Also, no significant differences in prolificacy were observed among the four intravaginal devices. These results indicate that the fertility of ewes treated with the four different intravaginal devices including a self-made P sponge and inseminated with frozen semen is similar, although the onset time of estrus and the LH surge varies with the use of progesterone-or progestogen-impregnated intravaginal devices.

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 (E 2 ), progesterone (P 4 ), 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. E 2 , P 4 , 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 E 2 peak after P sponge removal, but F1 did not show a clear preovulatory E 2 peak. The E 2 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 E 2 elevation. We concluded that a good ovarian response comparable to the multiple injection method can be achieved by the present simple superovulation method. Key words: pFSH, eCG, Superovulation, Ewes, Endocrine profiles.(J. Reprod. Dev. 44: [169][170][171][172][173][174][175][176] 1998) is necessary to inject it repeatedly [1], and the administration of decreasing doses gave more successful results than that administrating of a constant dose [2]. Multiple injections of FSH in decreasing doses resulted in increasing the number of corpora lutea, the number of recovered SH or eCG are gonadotropins widely utilized for induction of superovulation in ewes. Be-

Abstract. The incidence of premature corpora lutea (CL) regression was investigated in three different breeds (Merino x polled Dorset: MD, Suffolk: S, and South-Down: SD), parous and nonparous ewes (a total of 46 ewes) treated for superovulation during and out of the breeding season. Superovulation was induced with a single injection of 20 mg porcine follicle-stimulating hormone (pFSH) 2 days and 500 IU equine chorionic gonadotropin (eCG) 1 day, respectively before the removal of synthetic progestogen (40 mg FGA) vaginal sponges inserted for 12 days. All ewes were inseminated into the uterus with fresh-diluted or frozen-thawed semen by laparoscope, and a number of newly formed and regressed CL were recorded. Breed difference significantly (P<0.005) affected the incidence of premature regressed CL; S (6.3%, n=16) ewes were less in the proportion of the incidence of regressed CL than MD (37.5%, n=16: P<0.05) and SD (71.4%, N=14, P<0.01) ewes. The use of non-parous ewes and treatment during autumn tended to result in higher rates of incidence of premature CL regression than the use of parous ewes and treatment during spring. These results indicate that the incidene of premature CL regression in superovulated ewes was influenced by not only season and parity but also by breed of ewes used for superovulation treatment.

Abstract.Two experiments were conducted to enhance the corpus luteum (CL) function for increasing lambing rate of ewes treated with GnRH or hCG after artificial insemination (AI) during the non-breeding season. Ewes (Experiment 1: n=102, Experiment 2: n=37) were pretreated with a controlled internal drug release dispenser (CIDR) for 12 days and 500 IU equine chorionic gonadotropin (eCG) 1 day before CIDR removal. In Experiment 1, the ewes were treated on Day 12 (Day 0=CIDR removal): 1) Group I; GnRH (100 µg), 2) Group II; hCG (500 IU), 3) Group III; 0.6% saline (2 ml) for control. Pregnancy and lambing rates and prolificacy were not significantly different among the groups. But, there was significant (P<0.01) difference in the lambing rate between parous (27%) and non-parous (72%) in Group I. On Day 17, plasma progesterone (P4) levels of Group I were significantly (P<0.01) lower than those of Group III, but on the contrary, the plasma P4 levels of Group II were significantly (P<0.01) higher than those of Group III. In Experiment 2, the ewes were treated: 1) Group I; hCG (500 IU) on Day 6, 2) Group II; hCG (500 IU) on Day 9, 3) Group III; no treatment for control. Pregnancy and lambing rates and prolificacy were not significantly different among the groups, but on Days 12 and 15, the plasma P4 levels of Groups I and II were significantly (P<0.01) higher than those of Group III. The present results indicate that a single hCG treatment on Days 6, 9 and 12 after CIDR removal stimulates CL and increased P4 concentration, but the increased P4 levels did not reflect on the fertility of treated ewes.

No abstract