THE SEX-RATIO OF BOVINE EMBRYOS PRODUCED IN-VITRO IN SERUM-FREE OVIDUCT CELL-CONDITIONED MEDIUM IS NOT ALTERED

The sex ratio of bovine blastocysts produced in vitro in serum-free ov iduct cell-conditioned medium was investigated. Bovine embryos reachin g the blastocyst stage were removed from culture medium on Days 6, 7, 8 and 9 and were identified as small, mid-sized or expanded blastocyst s. One third (29/91) of the blastocysts appeared on Day 6. Twelve from them were small blastocysts (5 males), 7 were mid-sized blastocysts ( 4 males), and 10 were expanded blastocysts (5 males). On Day 7, 33 bla stocysts were obtained : 8 small (5 males), 9 mid-sized (3 males), and 16 expanded (13 males) blastocysts Finally, on Days 8 and 9, 29 blast ocysts were obtained : 12 small (9 males), 9 mid-sized (6 males) and 8 (3 males) expanded blastocysts. Sexing of the 91 blastocysts was perf ormed by using an original polymerase chain reaction (PCR) protocol ge nerating discreet internal control signals from both female and male s amples and Y-specific smears from the male samples. Proportions of mal e embryos on Days 6, 7 and on Days 8+9 were 48, 64 and 62%, respective ly. These values did not differ significantly among days and did not d iffer from 50%. Fifty-nine percent of small blastocysts, 52% of mid-si zed blastocyst and 62% of expanded blastocysts were male. No differenc e between these values or with respect to 50% could be observed. These results show that bovine blastocysts produced in serum-free oviduct c ell-conditioned medium do not have an altered sex ratio.