New approaches to increasing oocyte yield from ruminants

Artificial insemination, superovulation and embryo transfer have had benefi cial impacts on animal production but a limiting factor to realizing the fu ll potential of these techniques and of other reproductive technologies is the availability of fertile oocytes. To overcome this problem, methods for maturing oocytes in vitro (IVM) have been developed. The production of bovi ne embryos by IVM is in commercial use but the rate of success and quality of embryos is low. The lack of success may be due to the quality of oocytes that are being matured and it would be preferable to utilize the abundant source of immature oocytes from preantral and primordial follicles by devel oping systems for in vitro growth (IVG). Several culture systems that utili ze early growing follicles as a source of oocytes have been developed for l aboratory species and these have been successful in producing live young. I VG in association with IVM and cryopreservation have the potential to maxim ize the genetic potential of high genetic merit females and shorten generat ion intervals. This paper presents the current status of technology for the in vitro growth and development of immature oocytes, in vitro maturation a nd cryopreservation of germ cells in domestic ruminants.