IN-VITRO DEVELOPMENT OF PREIMPLANTATION EMBRYOS FROM DOMESTIC SPECIES

In recent years, the development of methods for the genetic manipulati on of domestic species has generated a rapidly increasing demand for p re-attachment embryos. The limited prolificacy of these species makes superovulation and surgical recovery of embryos necessary. However, th ese techniques are too expensive and labour-intensive to be used routi nely for supplying enough material for experimental or commercial appl ications. This has provided the thrust for an unprecedented effort to develop methods for the culture of embryos derived from in vitro matur ation and fertilization of oocytes collected from slaughtered animals. Offspring generated in vitro have been obtained using cattle, goats, pigs and sheep, but the efficiency and reliability of the techniques a nd the quantity of the embryos vary between species. At present, the b est results can be obtained in ruminants, while pig embryos have prove d to be more difficult to generate. Although many obstacles have been overcome simply by empirical trials and observations, the availability of high numbers of easily accessible embryos has also led to a substa ntial advance in our knowledge of their physiology. This has therefore widened the range of experimental models that can effectively be used in developmental studies, especially since, in some cases, models usi ng these species may be more relevant to human embryology than those u sing rodents.