Increase in calf production by the transfer of bisected bovine embryos

A total of 132 embryos were recovered from 17 superovulated donor cows 7 d after estrus. Seventy-four embryos were selected and assigned to 2 treatment groups. The number of whole embryos that were directly transferred (Group A) and bisected (Group B) were 44 and 30 embryos, respectively. Sixty demi-embryos were produced from 30 morulae to blastocyst-stage embryos that were bisected. One hundred-three embryos, including whole and demi-embryos without zonae pellucidae, were nonsurgically transferred. Only one whole or demi-embryo was transferred to each recipients. The pregnancy rate for whole embryos (A) was 63.6% (28/44), while for demi-embryos (B) it was 74.6% (44/59). There was no significant difference between the pregnancy rates of whole embryos (A) and bisected embryos (B) transferred 7 d after estrus. Forty-three calves including the 14 sets of identical twins were obtained from 30 original embryos (143.3%) using the embryo bisection technique.