Non-surgical embryo transfer in cattle embryo-recipient interactions

Results from 2286 non-surgical embryo transfers were analyzed to find relationships between embryo factors and recipient factors that affect pregnancy. Pregnancy rates from morulae (44%) and advanced morulae (53%) were reduced (P < .05) when compared to early blastocysts (65%), blastocysts (65%), blastocysts (66%) and advanced blastocysts (64%). Pregnancy rates from good quality Grade 1 embryos (64%) were higher (P < .05) than from Grade 2 (45%) or Grade 3 (33%) embryos. Pregnancy rates related to synchronization of estrus between donor and recipients are: -36 hrs. (before donor) (59%), -24 hrs. (61%), -12 hrs. (68%), 0 hr. (59%), +12 hrs. (61%), +24 hrs. (58%) and +36 hrs. (41%). Differences in pregnancy rate were significant for -12 hrs. (P < .01) and +36 hrs. (P < .01) recipients. Overall pregnancy rates in recipients on day 5 (48%), 5 1/2 (50%) and 6 (53%) were reduced (P < .02) when compared to day 6 1/2 (62%), 7 (63%), and 7 1/2 (66%) and 8 (62%). Pregnancy rates within each embryo stage of development were not related to synchronization with the donor cow (-36 hrs. to +36 hrs.) or the day of the recipient cycle (day 5 to 8).