title: Production of bovine identical twins via transfer of demi-embryos without zonae pellucidae.
abstract: Embryos were collected nonsurgically from nåturally-cycling or superovulated donors 7 d after estrus. Forty-four morulae, early blastocysts and blastocysts classified as good to excellent were bisected using a fine glass needle to produce forty-four identical demi-embryos. The bisected demi-embryos, without zonae pellucidae, were nonsurgically transferred, either by twin or single transfer. An additional forty-eight embryos were collected from the same donors and transferred as a control. Among the twin transfers, 8 of the 13 recipients became pregnant (61.5%). Seven of them conceived twin fetuses (87%) and one a single fetus. However, only two sets of normal identical twin calves were obtained. Among the single transfers, 72.6% (45/62) of bisected embryos without zonae pellucidae resulted in pregnancy, of which 48.4% (30/62) were identical twins, and 24.2% (15/62) were singletons. Another 27.4% (17/62) of the recipients did not became pregnant. The pregnancy rate for whole embryos with zonae pellucidae was 72.9% (35/48). These data show that there was no significant difference between the pregnancy rates of bisected embryos without zonae pellucidae and whole embryos with zonae pellucidae transferred 7 d after estrus. Bisection of bovine embryos was simplified and even morula stage embryos were transferred without zonae pellucidae.
authors.affiliation: Department of Theriogenology, Faculty of Veterinary Medicine, Hokkaido University, Sapporo (060), Japan.
authors.forename: N
authors.initials: N
authors.lastname: Seike
authors.forename: K
authors.initials: K
authors.lastname: Saeki
authors.forename: K
authors.initials: K
authors.lastname: Utaka
authors.forename: M
authors.initials: M
authors.lastname: Sakai
authors.forename: R
authors.initials: R
authors.lastname: Takakura
authors.forename: Y
authors.initials: Y
authors.lastname: Nagao
authors.forename: H
authors.initials: H
authors.lastname: Kanagawa