An important question regarding the use of transfer of
in vitro produced embryos is whether the alterations in
molecular, biochemical, and ultrastructural properties of
the embryo associated with culture [25] results in
a conceptus with reduced ability to complete normal
development in utero. There are reports that pregnancy
losses after initial pregnancy diagnosis are greater for
recipients of in vivo-produced embryos [26,27] or in vitroproduced
embryos [3] than for cows bred by AI. In other
reports, however, there were no differences in pregnancy
loss between cows pregnant as a result of ET or AI when
embryos produced in vivo [24] or in vitro [4] were transferred.
In the combined data set for the present study,
pregnancy loss for cows receiving embryos produced with
X-sorted spermwas higher than for TAI cows, but therewas
no difference in pregnancy loss between cows that received
embryos produced with nonsorted semen and TAI. There
are also a variety of abnormalities reported for calves born
as the result of transfer of an in vitro-produced embryo [28].
In the current study, there were no differences between TAI
and TET calves.