In vitro-produced bovine embryos: dealing with the warts.

Bovine in vitro embryo production is an inefficient process; while maturation and fertilization proceed apparently normally, the proportion of embryos reaching the transferable (blastocyst) stage is rarely over 40% and those that do reach this stage are often compromised in quality and competence. There is considerable evidence of a significant influence of follicular origin on oocyte developmental potential and it appears that once the oocyte is removed from the follicle its developmental capacity is capped. Evidence suggests that while culture conditions during bovine in vitro embryo production can impact somewhat the developmental potential of the early embryo, the intrinsic quality of the oocyte is the key factor determining the proportion of oocytes developing to the blastocyst stage. This paper highlights some of the problems associated with in vitro production of embryos and discusses some of the ways of overcoming these problems.