In Vitro Production of Equine Embryos1

Abstract

Successful techniques for in vitro maturation (IVM), in vitro fertilization (ITF), and in vitro culture (IVC) of equine embryos may become the ultimate method for producing large numbers of embryos. So far, however, there are no reports of pregnancies established from IVM oocytes. In the present study, our objective was to produce embryos, using strictly in vitro techniques, that have the capacity for successful uterine transfer. Oocytes aspirated from ovaries collected from an abattoir were subjected to IVM, IVF, and IVC, the latter in the form of coculture with oviductal epithelial cells. Sperm capacitation was accomplished through the use of either Ca2+ ionophore or heparin with ejaculated or epididymal semen. Maturation to metaphase II (M-II) was accomplished in 53-79% of the selected oocytes and fertilization or cleavage was observed in 15–26% of the oocytes when Ca2+ ionophore-capacitated ejaculated frozen/thawed semen was used. No fertilization or cleavage was obtained with the use of heparin-treated epididymal sperm. Two 8–16-cell embryos were obtained following IVM, IVF, and 72-h IVC; both of these were surgically transferred to the tip of the uterine horn of an unmated mare on Day 3 postovulation. Early pregnancy diagnosis performed on Days 10–14 revealed no pregnancy. We concluded that the method presented allows production of equine embryos in vitro provided that Ca2+ ionophore is used as capacitating agent.