Production of bovine androgenetic embryos and their in vitro-developmental potency

Androgenetic embryo is a useful model for investigating the contribution of the paternal genome to embryonic development. However, little work has been done with androgenetic embryo production in domestic animals. The aim of this study was to produce bovine androgenetic embryos efficiently and evaluate their in-vitro developmental potency. In experiment 1, we compared the developmental capacity of bovine androgenetic, parthenogenetic, and in vitro-fertilized embryos. To produce androgenetic embryos, in vitro-matured oocytes were enucleated and then fertilized in vitro with 5 x 10E6/ml of frozon-thawed spermatozoa at the same concentration as IVF. Early cleavage and blastocyst formation rates in androgenetic embryos (52.0% and 4.0%) were significantly lower (P0.05: chi-square test) than in IVF (78.9% and 35.9%) and parthenogenetic embryos (89.7% and 44.8%). In experiment 2, we investigated the in vitro development of androgenetic embryos derived from zona-free or zona-intact oocytes with different sperm concentrations (5 x 10E6 or 25 x 10E6/ml). When zona-free oocytes were used for IVF with 25 x 10E6/ml of spermatozoa, 40.0% of diploid embryos were obtained 15 h after IVF. Cleavage rate of zona-free oocytes inseminated with 25 x 10E6/ml of spermatozoa (78.3%) was significantly higher (P0.05) than that of zona-intact oocytes (54.1% and 60.0%), zona-free oocytes inseminated with 5 x 10E6/ml of spermatozoa (51.7%), or control IVF (65.4%). Blastocyst formation rate of zona-free oocytes inseminated with 25 x 10E6/ml of spermatozoa (11.7%) tended to be higher than those of zona-intact oocytes (4.9% and 6.2%) or zona-free oocytes inseminated with 5 x 10E6/ml of spermatozoa (5.0%), and did not differ significantly from control IVF (21.2%). These results suggest that developmental capacity of androgenetic embryos can be improved by using optimum sperm concentration and zona-free oocytes in cattle.