(sHLA-G) are associated with increased pregnancy and implantation rates (Fuzzi et al., 2002;

Noci et al., 2005; Sher at al., 2005; Desai et al., 2006). Moreover, a commercial ELISA kit that

can detect sHLA-G in culture samples has been developed and tested (Desai et al., 2006). In this

particular study, females that received at least one embryo that secreted sHLA-G had

significantly higher pregnancy and implantation rates compared to females that did not receive

any embryos positive for sHLA-G secretion (64% and 38% vs. 36% and 19%, respectively).

 In cattle, there are currently no markers or assays that can be used to select embryos based

on their capacity to survive after transfer. There is some potential for selecting blastocyst stage

embryos based on group II caspase activity (Jousan, 2006). Day 7 bovine blastocyst stage

embryos which are classified as having low group II caspase activity are more likely to hatch

following culture to day 10 than embryos that are classified as having high group II caspase

activity (45.5% vs. 24.5%, respectively). Although this procedure may have promise for

selecting embryos for transfer, further research is needed to determine whether group II caspase

activity (involved in apoptosis cascade) is predictive of embryo survival in vivo.

Modify Embryo Culture Conditions

 As described above, production of bovine embryos in vitro causes several alterations in

embryo morphology and physiology which have consequences for survival and development

after transfer. Recent studies using the sheep oviduct as a model for in vivo embryo

development have demonstrated the significant impact embryo culture conditions can have on

embryo developmental characteristics and post-culture viability (Enright et al., 2000; Lazzari et

al., 2002; Rizos et al., 2002; Lonergan et al., 2006). Thus, another strategy for improving the

survival of in vitro produced embryos following transfer is to modify embryo culture conditions

to more closely mimic the microenvironment found in vivo.