Sex of early bovine embryos was determined by polymerase chain reaction (PCR) using a single blastomere removed at the 16-32 cell stage. Embryos were produced in vitro and biopsied on the fifth day after in vitro fertilization. Biopsied embryos were cultured on a cumulus cell monolayer until embryo transfer. For the PCR, one pair of bovine-specific and one pair of Y-chromosome-specific primers were used. Definite signals following PCR amplification were obtained in 95.4% of cases indicating that one blastomere from a preimplantation bovine embryo is sufficient for sex determination by PCR. Nineteen biopsied embryos of predetermined sex were transferred into synchronized recipient females to examine their developmental potential in vivo. Ten of the recipients (52.6%) were found to be pregnant by ultrasonography 25 days after transfer. This result did not differ significantly from that achieved with the use of the control non-manipulated IVF embryos (54.1%; P > 0.1).

Contents Experiments have been performed to investigate the potential use of in vitro fertilization for the preservation of the endangered Hungarian Grey cattle. 1018 excellent quality oocytes from 167 ovaries of slaughtered Hungarian Grey cows and heifers were matured. Out of 966 oocytes cocultivated with pre‐test and swim‐up selected Hungarian Grey frozen‐thawed semen, 386 (39.9%) cleaved and 141 (14.6%) reached the morulablastocyst stage on the 7th day of embryo culture (1.69 transferable embryos per animal). Some embryos were transferred into the uterine horn of 10 natural cycling Hereford, Hungarian Red‐spotted, Hungarian Red‐spotted x Hereford recipients. Sixty days after transfer, 4 recipients were diagnosed as being pregnant by ultrasonography (two multiple births are expected); since then one calf has been born. Our results indicate that the IVF method can be used for the preservation of endangered cattle breeds, reducing the losses caused by slaughter for various reasons. Inhalt: In vitro Befruchtung beim ungarischen Grauvieh Es wurden Experimente durchgeführt, um die Möglichkeiten zu erforschen, die vom Aussterben bedrohte Rinderrasse Ungarisches Grauvieh über in vitro Befruchtung zu bewahren. 1018 Eizellen sehr guter Qualität wurden von 167 Ovarien geschlachteter Ungarischer Grauer Kühe und Färsen gereift. Von diesen wurden 966 Oozyten mittels vorgeprüftem und mit swim‐up selektiertem Grauvieh‐Sperma nach dem Auftauen kokultiviert. 386 (39,9%) der Oozyten teilten sich und 141 (14,6%) erreichten das Morula‐ bzw. Blastocystenstadium nuch 7tägiger Embryokultur (1,69 transferierbare Embryonen per Tier). Einige Embryonen wurden in das Uterushorn von 10 normal zyklischen Hereford, Ungarischem Rothvieh und der Kreuzungsrasse aus beiden übertragen. Sechzig Tage nach dem Transfer wurden 4 Tiere per Ultraschalluntersuchung als tragend diagnostiziert (zwei Mehrlingsträchtigkeiten wurden erwartet). Bisher ist ein Kalb geboren. Unsere Ergebnisse zeigen, daβ es möglich ist, mittels in vitro Befnrchtung bedrohte Ramen, wie das ungarische Grauvieh, zu erhalten und die Schlachtverluste, die aus verschiedenen Gründen möglich sein mögen, zu reduzieren.