Abstract
A tetraparental chimeric bull was successfully produced by aggregating bovine IVF embryos of F1 (female Holstein${\times}$male Japanese Black) and F1(female Japanese Brown${\times}$male Limousin) and culturing in vitro without the zona pellucida at Yamaguchi Research Station in Japan. In the microsatellite genotyping, 12% (28/228) microsatellite primer sets ware potentially useful for this parentage analysis in the chimeric bull, 78.6% (22/28) of microsatellite present in the chimeric bull were uniquely contributed from the Japanese Black and 21.4% (6/28) from Limousin. This chimeric bull semen was used in producing IVF embryos. The chromosome preparations were made from peripheral lymphocytes. Based on chromosome analysis the Chimera had apparently normal chromosomes (29 acrocentric pairs, one large sub metacentric X chromosome and one small sub metacentric Y chromosome). The proportion of acrosome reacted spermatozoa after 1 h of incubation was higher (p<0.01) with the Chimera than with the Holstein and in Japanese Brown bulls. But did not differ from Japanese Black and Limousin bull sperm. Fertilization rates observed after 5 h of sperm-oocyte incubation with Chimera sperm were higher (p<0.05) than with Japanese Brown and (p<0.01) than with Holstein sperm, but did not differ from Japanese Black and Limousin sperm. The cleavage rates of IVF oocytes inseminated with Chimera sperm were also higher (p<0.001) compared with Holstein, (p<0.01) Japanese Brown and (p<0.05) Limousin, but did not differ from Japanese Black sperm. The blastocyst rates of IVM oocytes inseminated with sperm were higher (p<0.05) than in Limousin, Japanese Brown and Holstein, but did not differ from Japanese Black. Chimeric cattles were produced by aggregation of parthenogenetic (Japanese Brown) and in vitro fertilized (Holstein) bovine embryos at the Yamaguchi Research Station in Japan and by aggregation of parthenogenetic (Red Angus) and in vitro fertilized (Holstein) embryos at the St. Gabriel Research Station in Louisiana. The aggregation rate of the reconstructed demi-embryos cultured in vitro without agar embedding was significantly lower than with agar embedding. The aggregation was also lower when the aggregation resulted from a whole parthenogenetic and IVF-derieved embryos cultured without agar than when cultured with agar. The development rate to blastocysts, however, was not different among the treatment. To verify parthenogenetic and the cells derieved from the male IVF embryos in blastocyst formation, 51 embryos were karyotyped, resulting in 27 embryos having both XX and XY chromosome plates in the same sample, 14 embryos with XY and 10 embryos with XX. The viability and the percentage of zonafree chimeric embryos at 24 h following cryopreservation in EG plus T with 10% PVP were significantly greater than those cryopreserved without PVP. Pregnancies were diagnosed in both stations after the transfer of chimeric blastocysts. Twin male and single chimeric calves were delivered at the Yamaguchi station, with each having both XX and XY chromosomes detected. Three pregnancies resulted from the transfer of 40 chimeric embryos at the Louisiana station. Two pregnancies were Jost prior to 4 months and one phenotypically chimeric viable male born.