Ovum pick-up in cattle: a 25 yr retrospective analysis

Repeated oocyte collection by transvaginal ultrasound-guided follicular puncture (Ovum Pick-Up: OPU), implicitly associated to in vitro embryo production (IVEP), has become alternative and competitive to superovulation for embryo production in cattle. It is alternative because it can be applied successfully irrespective of the reproductive status of the donor, i.e. in pregnant and acyclic animals, in those having patent tube or genital tract infections and in animals insensitive to superovulatory treatment. It is competitive because it can yield more transferable embryos per donor on a monthly basis. Through the years, the number of transferable embryos provided by OPU has significantly increased mainly due to the technological improvement of IVEP. However, limits to OPU application remain due to lower pregnancy rate of in vitro vs. in vivo produced embryos or non optimal cooperation between OPU practitioners and IVF laboratories. This review will focus on the technical modifications proposed for improving OPU efficiency, the analysis of the physiological parameters that affect OPU and IVEP efficiency and, finally, the use of OPU as a tool to study and manipulate reproductive activity in cattle.