Once daily versus twice daily treatments with follicle stimulating hormone in ewes synchronized with different doses of norgestomet

Abstract

Twenty mature, mixed-breed, seasonally anestrous female goats were used to study the effects of luteinizing hormone releasing hormone (LHRH) on ovulation rate, fertility, and blood progesterone levels following norgestomet-induced estrus and follicle stimulating hormone (FSH) treatments. Each goat received 6 mg norgestomet by subcutaneous (sc) implant and 3 mg intramuscularly, along with an intramuscular (im) injection of 5 mg estradiol valerate. Four injections of FSH were given for 2 d in divided doses of 10, 10, 5 and 5 mg im every 12 h, starting at 24 h before implant removal. The goats were randomly assigned to 1 of 2 equal treatment groups, and were treated with 2 intravenous (iv) injections of either 0.9% saline (control) or 300 ug LHRH at 24 and 48 h after the removal of the implants. All the goats exhibited estrus within 24 or 36 h of implant withdrawal and were mated to bucks of proven fertility. At laparotomy on Day 7 or 8 after the removal of the implants, the mean number of unovulated follicles was higher (P<0.05) in Group I than in Group II. The mean number of corpora lutea (ovulation rate), the total number of embryos and the number of normal embryos recovered were higher (P<0.05) in LHRH-treated does than in the controls. Treatment with LHRH resulted in 72.14% fertility (mean number of CL = 14) as compared with the controls with 64.29% fertility (mean number of CL = 2.8). The embryos obtained from goats in Group II were of more uniform developmental age regardless of the day of embryo collection, as compared with those of the controls. Plasma progesterone levels were significantly increased on Days 4 to 6 in both treatment groups. The results of this study have demonstrated that the FSH and LHRH treatment regimen increased follicular development, ovulation rate and blood progesterone levels in norgestomet-treated anestrous goats. Moreover, LHRH treatment enhanced fertility, and improved embryo quality as indicated by the significantly higher total number of embryos as well as the higher (P<0.05) number of normal recoverable embryos.