"Differential Cleavage Rate" in 2-day Litter Mate Rabbit Embryos.

Two-day litter mate embryos were obtained from superovulated rabbits, divided into slow- and fast-cleaving according to the number of blastomeres per embryo, and stored in 1:1 serum:saline at 10°C for 48 hr. Slow- and fast-cleaving embryos obtained from one donor were transferred into the 2 Fallopian tubes of one recipient. The recipients were laparotomized at 8 days p.c and autopsied at 29 days p.c. The viability of fast-cleaving embryos, as judged by per cent implants after storage, was higher than in slow-cleaving embryos. In most cases, 2-day embryos with more blastomeres had larger implants and heavier fetuses than embryos with less blastomeres; these differences were not statistically significant.