Reproductive biotechnologies: current status in porcine reproduction

During the past decade, considerable attention has been directed toward the development of reproductive technologies for both research purposes and for more controlled swine reproduction. Artificial insemination is an example of a technology that has continued to be expanded from early use in European countries to the USA and Canada where it is now estimated that a majority of the sows bred are artificially inseminated. In addition, several significant technological advancements have been made in the genetic modification of swine and interest has been generated in the possible use of swine as donors of specific tissues and of organs for the improvement of human health. At the same time, the systems for production of swine for human food continue to undergo major changes including, in some countries, the consolidation of swine into large, integrated units. These swine operations are very receptive to the use of technologies to reduce labor costs as well as a basis for increased production efficiency. Therefore, the combined interest in swine reproductive technologies by both the medical field and the swine industry creates an increased effort for the development of new technologies as well as for the implementation of existing ones. One of the more rapid technological advancements this decade has been the progress in in vitro production (IVP) of swine embryos. Major advancements have been made on the development of procedures for production of large numbers of embryos from oocytes collected at slaughter houses which are then matured (IVM) and fertilized (IVF) in the laboratory. Success in IVP has stimulated increased research in other areas that can be enhanced by the availability of embryos without a requirement for surgical collection from gilts or sows. One example is the combined use of IVF, gender-sorted sperm cells, and embryo transfer to produce offspring of a predicted sex. In a related area, instrumentation for non-surgical embryo transfer has recently been developed that results in significant improvement in this technology. Similar achievements have been gained in cryopreservation of embryos by vitrification. These developments will be reviewed with emphasis on the in vitro production of embryos from immature oocytes.