Cleavage, development and competence of sheep embryos fertilized by intracytoplasmic sperm injection and in vitro fertilization.

Abstract More abnormal fertilization has been found in sheep oocytes after intracytoplasmic sperm injection (ICSI) than after in vitro fertilization (IVF). Although the birth of a normal lamb has been reported, the efficiency of blastocyst production is low. We therefore evaluated the cleavage, development and viability of sheep embryos obtained from ICSI, IVF and sham injection. In vitro matured oocytes either injected or inseminated with spermatozoa were assessed for cleavage 1 and 4 d after injection or insemination, and for development to blastocyst after 7 d of culture. A total of 699 oocytes was injected (ICSI); 198 (30.6%) were activated and 55 (8.5%) developed to the blastocyst stage. Of the 17 recipient ewes with 1, 2, 3 or 4 embryos, 15 (88.2%) were pregnant on Day 18; of these 17 recipients, 7 (41.1%) and 6 (35.2%) ewes remained pregnant on Days 45 and 110, respectively. Two normal lambs were born, one ewe died on Day 110 with 2 normal male fetuses, another ewe aborted on Day 90 and 4 pregnancies were maintained. A total of 517 oocytes was inseminated (IVF); 296 (62%) were activated and 90 (18.8%) reached the blastocyst stage. A total of 19 ewes received 1, 2, 3 or 4 embryos; of these, 13 (68.4%) were pregnant on Day 18, and 8 (42.1%) ewes remained pregnant on each of Days 45 and 110. Three ewes delivered 5 lambs. Five pregnancies were maintained. A total of 156 oocytes was sham injected, 38 (24.3%) were activated and no blatocysts were obtained after culture. The results of this study showed that blastocysts obtained after ICSI are potentially viable and are not a result of parthenogenesis.