Transfer of split goat embryos without zonae pellucidae either fresh or after freezing.

Embryos in the morula to blastocyst stage were collected from superovulated goats either surgically or after slaughter. Embryos with good or fair morphology were bisected with a microblade without the aid of a holding pipette or other microinstruments. Of 103 morulae and 77 blastocysts that were split, 200 (97%) and 151 (98%) demi-embryos, respectively, with no major morphological aberrations were obtained. Zona-free demi-embryos derived from blastocysts were incubated in vitro for 2 h, and those derived from morulae for 24 h so that they would reach the blastocyst stage. Demi-embryos were transferred either fresh or after freezing and thawing. After 2 h of incubation, a significantly higher proportion of zona-free demi-embryos derived from blastocysts were of good quality than were zona-free demi- embryos derived from morulae (75 vs 45%). Seventy-six percent of zona-free demi-embryos derived from morulae developed to the blastocyst stage after 24 h in vitro. The quality of the embryos before splitting had a significant effect on the development of the demi-embryos in vitro. Transfer of 11 pairs of zona-free demi-embryos resulted in the birth of five twin and three singleton kids. Transfer of 11 pairs of demi-embryos frozen-thawed without zonae pellucidae resulted in the delivery of two singleton kids.