DEVELOPMENT OF INVITRO FERTILIZED OOCYTES FROM PREGNANT AND NONPREGNANT COWS IN OVIDUCTAL EPITHELIAL AND CUMULUS CELL COCULTURE SYSTEMS

The objectives of this study were 1) to measure cleavage, blastocyst formation, and blastocyst hatching after in vitro maturation (IVM), fertilization (IVF) and culture (IVC) of oocytes aspirated from pregnant versus nonpregnant cows, and 2) to compare embryo development in co-culture with bovine oviductal epithelial cells versus cumulus cells. No differences in cleavage (38 versus 40 %), blastocyst formation (13 versus 13 %), or blastocyst hatching (53 versus 51 %) were observed for in vitro-matured, fertilized, and cultured oocytes from pregnant versus nonpregnant cows, respectively (P > 0.05), indicating that nonpregnant and early-pregnant cows are equally acceptable donors of oocytes for IVM/IVF/IVC procedures. Cleavage (36 versus 40 %), blastocyst formation (11 versus 12 %), and blastocyst hatching (50 versus 55 %) were not different for embryos co-cultured with oviductal epithelial cells versus cumulus cells (P > 0.05). Thus, equivalent embryo development can be obtained with co-culture systems commonly used for in vitro-derived bovine embryos. These results help to define variables that affect comparison of results across laboratories and that are relevant to the practical application of IVM/IVF/IVC procedures to cattle.