Superovulation, embryo yield, quality, and embryo transfer in sheep

Two treatment regimens were used for superovulation of ewes during the repr oductive season. Merino ewes and Oxford Down ewes (n = 16) were superovulat ed with intravaginal sponges (40 mg Norgestomet, Intervet France, 14 days) and FSH-P (Folicotropin, Spofa Prague, total dose: 10 mg). Suffolk, Tsigai and Wallachian ewes (n = 21) were treated with CIDR (New Zealand, 14 days) - PMSG - Ovagen. FSH-P and Ovagen were administered twice daily for 4 days since Day 12 of the treatment period. Synchronizing devices (sponges, CIDR) were removed on Day 14 in the morning. Donors were mated by the selected r am using hand-service method (excluding Tsigai donors - group method). The following synchronization regimen was used in recipients: intravaginal spon ges (Norgestomet 30-35 mg, Intervet France, 17 days) - 500 I.U. PMSG (Sergo n, Bioveta Ivanovice in Hana) administered at time or sponge withdrawal. Sy nchronizing devices used in donor and recipient sets were withdrawn at the same time. Embryos were collected on Day 6 after 1st service and transferre d by the laparoscopic technique (Wolf, Germany). Low and non-significant di fferences (P > 0.05) were found between specific sets and regimens. Data on Tsigai ewes are not included in classification or superovulation response. In total, 120 embryos were transferred to 81 recipients, 57 ewes were preg nant (70.4%). Embryos survival rate determined by the obstetric control amo unted tu 61.7% (74/120), i.e. 1.3 lamb per lambed recipient. The increasing number of transferred embryos (1 up to 3) was associated with an increasin g number of lambs - a negative tendency was evident, however, in embryo sur vival rate. Data characterizing transfer of cryopreserved embryos are orien tational. Pregnancy rates in recipients of vitrified embryos, fresh ones, a nd embryos preserved by the conventional method (in the freezer) amounted t o 60.0 (3/5), 66.7% (2/3), and 22.2% (4/18), respectively (P < 0.05).