From cattle to sheep: a view of the difficulties and success of commercial in vitro production of sheep embryos

ABSTRACT

The in vitro production (IVP) of sheep embryos, unlike that for cattle, requires hormonal treatment with progesterone or a progestagen to improve efficiency of ovum pick - up (OPU). Another difference is that the process used to obtain oocytes is by OPU in cattle and LOPU (laparoscopic ovum pick - up) in sheep. Several factors affect oocyte recovery, including the skill of the technician, suction pressure and the aspiration system for LOPU. The LOPU technique is less invasive and can be p erformed weekly, biweekly or monthly in ewes. LOPU is an option to MOET (multiple ovulation and embryo transfer), mainly for animals of high genetic value that do not respond to the superovulatory treatment or only produce unfertilized oocytes. The embryos in the initial development stages can be transferred into the oviduct or into the cranial portion of lumen of the uterine horn, reducing the time for in vitro culture, which can be harmful to embryos. Although early results are promising, there are still many points to be improved in IVP of sheep embryos before it is used extensively in the commercial sheep industry.