Factors Affecting Embryo Transfer Success in Recipient

Recipient age at transfer (less than 525 d old or more than 525 d old), season (fail, winter, spring, summer), method of synchronization (natural or induced), and transfer technique (surgical or nonsurgical transfer) were associated with success of embryo transfer in a log-linear analysis. In a separate analysis, no significant association was found between success of transfer and transfer to the left or right uterine horn. Summer had the lowest proportion of successful transfers (58.9%). Pregnancy rates were 83% using the surgical transfer method and 68% with transcervical transfers. Proportion of pregnancies following a second transfer was not different from the proportion after first transfers. Success of embryo transfer was highest if recipients were >525 d old and if transfers were performed surgically in spring following synchronization of recipients with cloprostenol, an analog of prostaglandin F 2 a. Probability of success was lowest for transfers to young, prostaglandin-synchronized recipients, performed nonsurgically in summer. Received October 28, 1985. LEON O. WEAVER and JOHN GALLAND University of California Veterinary Medicine Teaching and Research Center School of Veterinary Medicine 18830 Road 112 Tulare 93274 UDI SOSNIK Maddox Dairy Burrel, CA 93607 PETER COWEN North Carolina State University Department of Microbiology Pathology and Parasitology School of Veterinary Medicine 4700 Hillsborough Street at William Moore Drive Raleigh 27606