Bovine superfetation by natural conception secondary to an embryo transfer pregnancy

There was only one embryo transferred to the recipient female. There was no chance for natural service to occur from 21 days prior to the transfer of the embryo to 31 days after the transfer of the 7 day old blastocyst. The surrogate female was palpated as being 38 days pregnant 31 days after the transfer of a 7 day old embryo by an experienced professional before being exposed to the natural service sire. The second fetus was of a different sex than the first and was approximately 60 days less mature. All other pregnancies within this well managed herd were accounted for and no other cows calved within the area close to that time. The remaining recipients carried pregnancies to the approximate expected calving date. Conclusion. This case report should support earlier evidence that superfetation in the bovine can and does occur.