抄録
The effects of doses of porcine follicle-stimulating hormone (pFSH) and equine chorionic gonadotropin (eCG) for a simple superovulation method in ewes were investigated on ovulation rate, proportions of fertilized oocytes and normal embryos at recovery. The ewes were treated with intravaginal sponges impregnated with fluorogesterone acetate (FGA) for 12 days. For superovulation, an intramuscular injection of pFSH was given at 48 h before sponge removal, and eCG was given at 24 h after the pFSH injection. In Trial 1, the ewes (n=28) were divided into two groups. Group A (n=14) received 20 mg pFSH and 250 IU eCG, and Group B (n=14) was treated with 15 mg pFSH and 500 IU eCG. The effect on different breeds (Suffolk: Sf, Merino × polled Dorset: MD, South-Down: SD) was also investigated. In Trial 2, the ewes (n=20) were divided into 4 groups with different doses (0: control, 100, 200, 300 IU) of eCG combined with a 20 mg pFSH injection. All ewes were inseminated into the uterus with fresh-diluted or frozen-thawed semen by laparoscope, and the numbers of newly formed and regressed corpora lutea were recorded. Embryos were recovered on Day 6 or 7, and morula and blastocyst stage embryos were observed as being normal. There were no significant differences in the mean ovulation rates between Groups A (23.7 ± 21.5) and B (16.3 ± 9.8), and among the three breeds of ewes. The rates of fertilized oocytes and normal embryos were significantly higher in Group A than Group B (Trial 1). The ewes treated with 200 or 300 IU eCG had significantly shortened time-intervals from sponge removal to the onset of estrus and had higher ovulation rates than controls (Trial 2). The present study indicates that an appropriate eCG dose combined with a single injection of 20 mg pFSH would be 200-300 IU for a simple superovlation method in ewes pre-treated with progestogen-impregnated vaginal sponges.
