To some
extent, the experimental design also facilitated the likelihood
of viral transmission to embryo donors and recipients
and its detection because: (1) the embryo donors were
exposed to a relatively high titer of virus via two inseminations;
(2) two embryos were transferred into each
recipient on many occasions; (3) fresh embryos were
transferred; and (4) fresh embryos were tested for thepresence of infectious virus. Nevertheless, in most respects,
our experimental approach closely mimicked the usual
procedures in ET practice, and recommendations given in
the IETS manual [4,20] and OIE [14] for the production and
transfer of in vivo-produced embryos were followed.
Particular attention was paid to washing fertilized and
degenerated embryos because it might indicate the
potential effectiveness of the decontamination procedure
of embryos selected for ET [20]. However, trypsin treatment
was omitted in our washing protocol because this has
not been shown to be consistently effective for the removal
of BVDV from embryos [22,23].