10 In vivo embryo production of superovulated maiden Dohne Merino ewes and embryo transfer under high-altitude conditions

We have proposed that increasing the living standard in Peruvian High Andes peasant communities should be based mainly on improving the productivity of their sheep production flocks. For this purpose, we have been implementing a reorientation program of genetic ability, introducing from Australia via embryo transfer (ET) the Dohne Merino dual-purpose sheep breed (Vivanco et al. 2018 Spermova 8, 133-137). The objective of the present study was to assess the in vivo embryo production potential of Dohne Merino ewes born and reared at high altitude. Five 18-month-old maiden ewes born from imported embryos and reared (grazing system in natural range lands) at high altitude at Chagas Chico ranch in Lancari, Pasco, Perú (10.8°S 76.5°W; 4516 m elevation) were selected as embryo donors and subjected to the following superovulatory regime: Day 0 a.m., intravaginal insertion of medroxyprogesterone acetate (MAP) 60 mg sponge (Progespon®; Zoetis) and injection of prostaglandin F_2α (1 mL Sodic Cloprostenol, 263 μg mL⁻¹, Ciclase DL®), Day 7 a.m., replacement of the MAP sponge for a new one; Day 7 p.m., first injection of FSH, then injections of FSH every 12 h decreasingly; on Day 10 a.m., in addition to the sixth injection of FSH, 160 IU of equine chorionic gonadotrophin was injected (eCG; Novormon®, 5000 IU eCG; Zoetis), the MAP sponge was removed, and teaser rams with crayon markers were introduced. Heat was checked from Day 10 p.m. onwards every 12 h, and ewes not in heat continued receiving FSH. On average, donors received 220 mg of Folltropin. Ewes detected on heat were not injected and were isolated for insemination via cervical with fresh diluted ram semen 12 h after being detected in heat. At 3.5 days after insemination, all ewes received a new MAP sponge that remained inserted in the donor’s vagina until the time of embryo flushing to prevent embryo loss in case of luteal regression. Embryos were flushed on Day 7 post-insemination by surgical laparotomy and were handled and graded as per IETS recommendations. The total number of structures recovered was 35 (average of 7.0 ± 4.7 per donor flushed); of those, 31 (88.6%) were grade 1 and 2 transferable embryos (average of 6.2 ± 4.3 embryos per donor flushed). We conclude that the Dohne Merino ewes show good performance for in vivo embryo production under high-altitude conditions, and their embryo production per donor is the same as that reported elsewhere under sea-level or lower-altitude conditions.