Factors affecting embryo transfer success in recipient heifers under field conditions

Recipient age at transfer (less than 525 d old or more than 525 d old), season (fall, 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 greater than 525 d old and if transfers were performed surgically in spring following synchronization of recipients with cloprostenol, an analog of prostaglandin F2 alpha. Probability of success was lowest for transfers to young, prostaglandin-synchronized recipients, performed nonsurgically in summer.