Abstract
Two trials were conducted to investigate the effects of the number of follicle stimulating hormone (FSH) injections combined with pregnant mare serum gonadotropin (PMSG) on ovulation and recovery rates, normality and freezability of recovered embryos. Eleven Corridale ewes (Trial 1: October 1994, Trial 2: December 1994 [1 ewe excluded]) were treated with a vaginal sponge containing 60 mg 6-methyl-17-acetoxyprogesterone (MAP) for 12 days. In 2 trials, 3 days before sponge removal, superovulation was induced using 20 mg of FSH, administered in either a single injection or twice daily over a 3-day period in a decreasing dosage (multiple), in combination with PMSG (500 I.U.). In Trial 1, estradiol-17β (E2) and luteinizing hormone (LH) were measured to evaluate the endocrine response to FSH injections in the 2 superovulation methods. In both trials, there were no significant differences in ovulation and recovery rates (Trial 1: single=17.5 ± 4.1, 69.4% vs multiple=23.0 ± 1.9, 57.4%; Trial 2: single=19.2 ± 5.5, 58.3% vs multiple=19.6 ± 5.7, 57.1%) between the treatments. There were also no significant differences on the numbers of normal and freezable embryos. There were no significant differences in the levels of E2 and LH except the levels of LH at 6 h and 8 h after sponge removal for multiple FSH injection were higher than they were for the single injection (P<0.05). This suggested that the number of FSH injections did not affected the endocrine response in the superovulated ewes during the breeding season. In conclusion, FSH administered in a single injection together with PMSG was as effective as the same total dosage of FSH administered in 6 injections over a 3-day period.
