Embryo transfers done in small ruminants are a fraction of those recorded for cattle Embryo Transfer in Cattle Although collection of a single embryo is occasionally done in cattle, most embryo transfers in cattle are done after a hormonal treatment to superovulate donor cows and to maximize recovery... read more . Globally, 1.3 million embryo transfers were reported for cattle in 2018, and only 17,868 were reported for sheep and 8,157 for goats during the same period. In addition to commercial and market factors limiting the production of embryos in small ruminants, current embryo transfer techniques in sheep and goats almost exclusively consist of surgical or laparoscopic methods for embryo collection and transfer.
Donor and recipients are synchronized using progestagens with an injection of prostaglandin F2alpha administered on the day the intravaginal progestagen device is inserted. Because of the additional superovulation hormonal treatment donor females receive, recipients come into estrus earlier than donor ewes and does; therefore, the progestagen source (typically an intravaginal device) in recipients is removed 12 hours before it is removed in donors.
Follicle-stimulating hormone is commonly used to superovulate small ruminants. As in cattle, FSH is commonly administered twice daily in a series of decreasing doses administered over 3 days (eg, 5 mg every 12 hours on day 1, then 3 mg every 12 hours on day 2; and then 2 mg every 12 hours on day 3). On the last day of FSH treatment, the progestagen source is removed and a luteolytic injection of PGF2alpha administered. Estrus is typically detected by use of vasectomized bucks or rams; artificial insemination should take place 12–24 hours after estrus is detected or 45–50 hours after progestagen removal. Intracervical or transcervical artificial insemination is difficult and requires advanced training and practice. Increased pregnancy rates are obtained by laparoscopic artificial insemination because it allows the semen to be deposited in the cranial aspect of the uterine horns.
Surgical embryo collection is still very common; however, laparoscopic and nonsurgical transcervical catheterization procedures are consistently improving and producing good results, albeit still lower than those obtained with surgical methods. Embryos are collected 7–8 days after estrus.