Note: This is the fourth in the series of topics suggested by the AETA Board of Directors. Should any readers want to suggest future topics, please email them to me.
John F. Hasler
Where does the transferred embryo have to be placed in order to maximize pregnancy rate?
Well, we know where a bovine embryo belongs when it first travels through the UT junction! Initially, it will be in the tip of the uterine horn, and if the embryo resulted from fertilization of the animal’s own ovulated oocyte, then the embryo will be in the horn on the same side (ipsilateral) as the CL. However, that is not necessarily where the embryo will end up and implant. Embryo migration within the uterus is well-known in litter producing domestic animals, such as swine, but it also has been shown to occur in single ovulating cattle at a frequency of 2 to 3% (for review see McMillan and Peterson, 1999), although Scanlon (1972) reported no trans-uterine migration in more than 600 single ovulating cows. He did, however, note that a series of previous published reports indicated a migration percentage of 0.3 to 1.6%. Migration has not been reported in cattle following the non-surgical transfer of a single embryo transferred to the horn either to the ipsilateral or contralateral to the ovary with the CL, although the sample sizes were small. (more…)
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