Control of ovarian function for in vivo and in vitro embryo production

Abstract

Knowledge of follicular wave dynamics through use of real-time ultrasonography and development of the means by which follicular wave emergence can be controlled have provided new practical approaches to superstimulation of donors for in vivo and in vitro embryo production. Although some embryo transfer practitioners still initiate superstimulatory treatments during midcycle, elective control of follicular wave emergence and ovulation have greatly impacted on-farm embryo transfer, especially when large groups of donors need to be superstimulated concurrently. A combination of estradiol and progestins has been the most common treatment for synchronization of follicular wave emergence for many years. However, in countries where estradiol cannot be used, practitioners have turned to alternative treatments, e.g. mechanical follicle ablation or gonadotropin releasing hormone administration, for synchronization of follicle wave emergence for superstimulation. In vitro embryo production also depends on synchronization of follicle wave emergence. As Bos indicus cattle have high antral follicle populations, large numbers of oocyes can be obtained by ovum pick up without superstimulation. However, in Bos taurus donors, synchronization of follicular wave emergence and superstimulation with follicle stimulating hormone is necessary to obtain high numbers of oocytes by ovum pick up and blastocysts following in vitro fertilization. Treatments for synchronization of follicular wave emergence and superstimulation are practical, easy to administer by farm personnel and facilitate application of both in vivo and in vitro embryo technologies in cattle.