Abstract
A methodological investigation was conducted on chromosome preparation from bovine blastocysts developed in vivo, which were obtained from superovulated cows, and those developed in culture after in vitro fertilization of in vitro matured oocytes. The rate of sexing and the incidence of numerical abnormality of chromosomes were also examined.
In the embryos developed in vivo, the length (2 to 8h) of colcemid-treatment (TCM 199 containing 0.04μg/ml colcemid) did not affect the percentage of embryos with metaphase plates and the rate of sexing. In the embryos developed in culture, a 2-h colcemid-treatment gave the highest percentages of embryos with metaphase plates and the highest sexing rate.
In the embryos developed in culture, a brief rinsing of embryos in a hypotonic solution of 0.5% sodium citrate prior to a hypotonic treatment with 0.5% sodium citrate for 5min gave a higher rate of sexing as compared with the rate obtained by the second hypotonic treatment only. A similar trend was observed in the embryos developed in vivo. From these results, it was concluded that the brief rinse of embryos prior to the hypotonic treatment is the most desirable to obtain high quality chromosome preparations.
The sexing rates of embryos were not different according to their developmental stages. The percentage of embryos with metaphase plates and the sexing rate tended to decrease as the quality of embryos becomes poor. The incidence of embryos with abnormal numbers of chromosomes was higher in the embryos developed in culture after in vitro fertilization than in those developed in vivo.
