@conference {40633,
	title = {In vitro production of cattle embryos: Use in beef twinning programmes.},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {54},
	year = {1994},
	month = {Jan},
	pages = {351-352},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	abstract = {This study investigated the survival of <I>in vitro</I> 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 <I>in vitro</I>  
derived embryos, embryo survival drops during early pregnancy.  Current research  
efforts are investigating factors that may influence early embryo survival in  
cattle. },
	issn = {1176-5283},
	author = {Pugh PA and Thompson JG and McGowan LT and McMillan WH and Tervit HR}
}
