Development of bovine embryos in single in vitro production (sIVP) systems

Single in vitro production (sIVP) of embryos enables the study of developmental parameters of individual oocytes or embryos. Because several previously published sIVP systems showed varying levels of success, we attempted to design a simple, semidefined sIVP system that resulted in developmental rates similar to those obtained through group production (gIVP). In a 5 x 3 x 4 factorial experiment, 4200 oocytes were randomly assigned to combinations of various maturation (sIVM), fertilization (sIVF), and culture (sIVC) treatments based on media TCM199 (5 treatments), TALP (3 treatments), and SOF/aa/BSA (4 treatments), respectively. All sIVP steps were carried out in 10-12 microl drops under oil. Embryo development to blastocyst on days 7 and 8 of culture was determined and blastocyst cell numbers measured as an indicator of embryo quality. No interaction was found within any combination of sIVM, sIVF and sIVC treatments. Also, there was no difference in percentage of development to various stages for embryos in any of the sIVM or sIVF treatments (over all treatment combinations). However, when treatment combinations included charcoal-treated serum addition on day 5 of culture, a significant increase in development (39.0% total blastocysts/total oocytes vs. 22.7, 23.8 and 23.5% for the other 3 sIVC treatments, respectively; P < 0.001) and decrease in mean cell number (114.2 vs. 149.1, 150.5 and 143.7 cells, respectively; P < 0.001) was observed. These results are comparable to those routinely obtained in this laboratory with gIVP and establish standard conditions for individual embryo production.