Estradiol-17 beta-oxytocin-induced cervical dilation in sheep: Applicationto transcervical embryo transfer

Experiments were conducted to determine whether exogenous estradiol-17 beta (E2) and oxytocin (OT) can be used to improve transcervical (TC) embryo tr ansfer (ET) procedures for sheep. Our concerns that the E2-PT treatment may alter luteal function prompted Exp. I, in which 32 ewes were assigned to t reatments in a 2 x 2 factorial array. On d 7 after onset of estrus, ewes re ceived i.v. either 100 mu g of E2 or diluent; 12 h later, ewes received i.v . either 400 USP units of OT or saline. To monitor luteal function, progest erone was measured in jugular blood collected from d 7 to 18. The treatment s did not affect progesterone concentrations. Two trials were conducted in Exp. 2. In Trial 1, ewes were assigned to one of three treatments: TC trans fer with E2-OT treatment to dilate the cervix, laparoscopic ET with E2-OT t reatment, or laparoscopic ET with an equivalent diluent that did not dilate the cervix. In Trial 2, ewes were assigned to treatments in a 2 x 2 factor ial array: TC or laparoscopic ET on d 6; E2-OT treatment for cervical dilat ion or diluents on d 6. Transferred embryos were recovered on d 12 in Trial I and d 14 in Trial 2, evaluated morphologically for development, and scor ed. Treatments did not affect the percentage of transferred embryos recover ed. However, mode of transfer decreased (P < .01) the mean embryo developme nt score. The EB-QT treatment increased (P < .01) the development score of embryos transferred transcervically, indicating that cervical dilation may improve the chances of embryos surviving after TC transfer. In conclusion, E2-OT treatment did not affect luteal function, and the E2-OT treatment can be used to enhance the success of TC embryo transfer in sheep.