CHROMOSOMAL ANALYSIS OF 159 BOVINE EMBRYOS COLLECTED 12 to 18 DAYS AFTER ESTRUS

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Abstract
Embryos (159) were analyzed in conjunction with embryo transfer studies. Chromosome preparations were made from small biopsy fragments of trophoblast, from large portions of trophoblast and the inner cell mass, or from the entire embryo. Results obtained from fragments were similar to those obtained from large portions of trophoblast and inner cell mass. No structural chromosomal abnormalities were observed. Single triploid, diploid-triploid and diploid-hexaploid and 66 diploid-tetraploid embryos were found. The 41.5% incidence of diploid-tetraploid embryos was relatively high, and appeared to be associated with a donor factor. The transfer of 49 biopsied and analyzed embryos to recipients resulted in 15 pregnancies, 7 with diploid-tetraploid embryos having up to 25% of polyploid cells. The diploid-triploid and diploid-hexaploid embryos were among the transfers that did not result in pregnancy. The low incidence of embryos with chromosomal anbormalities, excluding the diploid-tetraploid embryos, may have been due to the embryos being analyzed at 12-18 days of age rather than at an earlier age before death or degeneration could have occurred.