Effect of time interval from insemination to first cleavage on the developmental characteristics, sex ratio and pregnancy rate after transfer of bovine embryos
In vitro produced bovine zygotes show substantial variation in the time required to complete the first cell cycle and in their in vitro development potential. A number of reports have highlighted the fact that the fastest developing embryos in vitro are most likely to be comparable with their in viv...
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Published in | Journal of reproduction & fertility Vol. 117; no. 1; pp. 159 - 167 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
England
Society for Reproduction and Fertility
01.09.1999
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Subjects | |
Online Access | Get full text |
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Summary: | In vitro produced bovine zygotes show substantial variation in the time required to complete the first cell cycle and in their in vitro development potential. A number of reports have highlighted the fact that the fastest developing embryos in vitro are most likely to be comparable with their in vivo counterparts. At 24 h after IVF, presumptive zygotes were cultured in droplets of synthetic oviduct fluid medium. Droplets
were examined at regular intervals and all cleaved embryos at each time point were transferred into new droplets and cultured
separately for the duration of the experiment. All uncleaved zygotes were returned to the incubator and re-examined at the
successive time points until 48 h after insemination, at which time the remaining uncleaved oocytes were retained as a group.
A representative number of day 7 blastocysts from zygotes that had cleaved by 30 or 36 h were transferred to synchronized
recipients and pregnancy was diagnosed by ultrasonography at day 35. Glucose and glutamine metabolism was examined in zygotes
and blastocysts and compared retrospectively with time of first cleavage. A representative number of blastocysts from each
of the cleavage groups was sexed using PCR. Data were analysed by chi-squared and regression analysis. Development to the
blastocyst stage decreased as the time from insemination to first cleavage increased ( r = 0.97, P < 0.03). There was no difference in blastocyst hatching, number of blastocyst cells or pregnancy rate between the
30 and 36 h groups. The overall sex ratio was 62% males ( n = 258, P < 0.0001) and was not different in the 30 and 36 h groups (61%, n = 155 versus 63%, n = 95, respectively). These results indicate that although time of first cleavage has a major influence on the probability
of an embryo developing to the blastocyst stage, once that stage is attained, subsequent developmental characteristics are
unrelated to the time of first cleavage. |
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ISSN: | 1470-1626 0022-4251 1741-7899 |
DOI: | 10.1530/jrf.0.1170159 |