Aspects of in Vitro Fertilization and Embryo Culture in Domestic Animals2

Various aspects of the major components of in vitro fertilization and embryo culture in domestic farm animals are discussed. An examination of the spermatozoa and oocyte incubation media showed no media or protein supplement to be superior in promoting in vitro fertilization in cattle, sheep or swine. Generally, ovulated oocytes or activated follicular oocytes were penetrated by sperm more frequently than were immature oocytes. Spermatozoa that were incubated in vivo or in the oviducts of a different species generally achieved higher oocyte penetration than did spermatozoa incubated in vitro. In most in vitro fertilization studies, an in vivo component was introduced, generally oocyte or sperm maturation, which served to confound analysis of the in vitro results. Furthermore, the relatively low level of success and high incidence of chromosomal abnormalities with in vitro fertilization in other species require that careful and complete studies analyzing the components of in vitro fertilization in domestic farm animals be conducted. The culture of embryos from domestic farm animals is detailed, with emphasis on in vitro conditions and rate of success. As with laboratory animals, bovine, ovine, porcine and caprine embyos of fewer than eight cells are more difficult to culture to the blastocyst stage than are older embryos. When placed in culture, morulae from these species commonly form blastocysts, and in vitro hatching has been reported, except for caprine embyos. Embryo development has been reported to occur in a variety of culture conditions, media and supplements and gaseous atmospheres. Culture in sealed tubes yields results equal to those reported for microdrops of media under paraffin oil. Ham's F-10 medium appears to be the medium of choice for bovine embyros, with a variety of simple media working about equally well for ovine, porcine and caprine embryos. There appears to be little advantage in supplementing media with more than 10% heat-treated serum, but optimal concentrations of bovine serum albumin remain to be determined. A reduced oxygen atmosphere of 5% CO2, 5% O2, 90% N2 is at least equal and, in some species, superior to 5% CO2 in air in promoting embryo development.