This study investigated the survival of in vitro derived embryos as single or twin pregnancies following their twin transfer to recipient cows. Abattoir-derived oocytes were matured, fertilised and then cultured for 6-7 days using our standard laboratory procedures. One hundred and forty good quality late morula and blastocysts were transferred non-surgically, in pairs, to recipient cows on day 7 of the oestrous cycle (day 0 = oestrus). Recipients were monitored by ultrasound for pregnancy up to Day 60 and embryo survival was determined. While 57 (81%) of recipients did not show oestrus by day 21, only 39 (56%) were pregnant on day 35 and 30 (77%) of the pregnancies were twins (embryo survival; 57%). Increasing stage of gestation was associated with a decrease in pregnancy rate, twin pregnancies and embryo survival (46%, 37% and 31%, respectively) on day 60. The results show that while high initial pregnancy rates can be established following the transfer of two in vitro derived embryos, embryo survival drops during early pregnancy. Current research efforts are investigating factors that may influence early embryo survival in cattle.
Proceedings of the New Zealand Society of Animal Production, Volume 54, , 351-352, 1994
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