In vitro embryo production from cumulus-oocyte complexes type II in Bos indicus cattle

The morphological selection of cumulus-oocyte complexes (COCs) is animportant step for in vitro embryo production. It has been suggested thatCOC showing signs of atresia have the ability to generate embryos. Theobjective of this work was to evaluate the effect of COC morphology fromBos indicus animals with signs of early atresia versus no signs of atresiaon in vitro embryo production. COC were classified in: Type I (TI): homogeneousooplasm with ≥ 4 layers of compact cumulus cells (CC) and Type II(TII): granular ooplasm and ≥ 4 layers of CC slightly expanded. The COCwere matured in vitro for 24 hours in TCM199 medium and subsequentlyfertilized in vitro for 18 h. The suspected zygotes were cultured in vitro forseven days in modified SOFaa medium. Embryonic quality was determinedby blastomeric count following staining with Hoechst 33342. Student testwas used to determine statistical differences for cleavage, blastocyst rateand blastomeric counts between types of COC. The cleavage rate for TI (n= 220) and TII (n = 161) was 88 ± 4 % and 89 ± 8 % respectively (p> 0.05);embryo development rate was 36 ± 7 % and 33 ± 8 % (p>0.05) respectively.The blastomeric count for both groups was 101 and 104 cells for TI and TIIrespectively (n = 10), (p>0.05). These results demonstrate that there is nodifference in the quantity and quality of embryos produced in vitro usingCOC type I or type II, suggesting that both types could be used for bovine invitro embryo production in Bos indicus cows.