The blastocyst production rate and incidence of chromosomal abnormalities by developmental stage in in vitro produced porcine embryos.

摘要

The study was conducted to determine the relationship between embryonic development speed at different stages (the cleaved stage at 52 h and the blastocyst stage at 6 days post insemination) and incidences of chromosome abnormalities in in vitro produced porcine embryos. Porcine oocytes were collected from 3-6-mm ovarian follicles obtained at a slaughterhouse and matured in modified NCSU-37 medium for 44-46 h. Following in vitro fertilization with a final concentration of 1x105 sperm/ml for 3 h, all oocytes were cultured in vitro for 52 h. Day 2 (52 h after insemination) embryos were classified according to their cleaved stages into 2-cell, 3- to 4-cell, 5- to 8-cell, and >8-cell stages, and were cultured separately for an additional four days (Day 6). The resultant Day-6 blastocysts were classified according to their diameter: Grade A, expanded blastocysts; Grade B, expanding blastocysts; and Grade C, early blastocysts. The chromosomes of the blastocysts were then analysed. The 3- to 4-cell and 5- to 8-cell embryos had significantly higher blastocyst development rates (46.1 and 36.9%, respectively), and these blastocysts contained significantly more cells (40.2 and 42.4 cells, respectively) than those derived from 2-cell embryos and >8-cell embryos (28.6 and 26.5 cells, respectively). The incidence of chromosomal abnormalities was significantly higher in the blastocysts derived from 2-cell and >8-cell stage embryos than in blastocysts derived from the other stage embryos. The grade A blastocysts had the lowest incidence of chromosomal abnormalities (35.3%) and contained the highest number of cells (48.7 cells). It is suggested that porcine in vitro production (IVP) yields a high blastocyst rate and an excellent embryo quality when 3- to 4-cell and 5- to 8-cell stage embryos are selected on Day 2 after insemination. The same criteria yield a higher quality of expanded blastocysts based on the stage of embryo development and morphology.