In vitro fertilization and development of frozen-thawed bovine oocytes.
Bovine oocytes were vitrified (V-oocytes) or frozen slowly (S-oocytes) at the germinal vesicle (GV) stage or after maturation in vitro (IVM) and their survival assessed morphologically and also by in vitro fertilization (IVF) and culture. The morphological survival of S-oocytes was 30.7% after freezing at the GV stage and 53.3% after IVM. The corresponding survival rates of V-oocytes were significantly lower, viz. 14.6 and 14.0%, respectively. The fertilization rate of S-oocytes frozen after IVM (51.0%) was lower than that of unfrozen controls (75.8%), but higher than after other treatments. Development continued in 16.0% of the fertilized S-oocytes, compared to 39.4% of control IVF zygotes and 1.6% developed into morulae or blastocysts (4.5% in controls). Only 0.8% of frozen-thawed GV stage oocytes and 4.6% of post-IVM V-oocytes cleaved after IVF and none formed morulae or blastocysts. Transfer of four embryos (two morulae and two blastocysts) derived from post-IVM S-oocytes into a recipient heifer resulted in pregnancy and the birth of twin calves.
Fuku
E
E
Department of Animal Science, McGill University, Ste. Anne de Bellevue, Quebec, Canada.
Kojima
T
T
Shioya
Y
Y
Marcus
G J
GJ
Downey
B R
BR
D000818:Animals; D002417:Cattle; D002470:Cell Survival; D015925:Cryopreservation; D004624:Embryo Transfer; D005314:Embryonic and Fetal Development; D005260:Female; D005307:Fertilization in Vitro; D009865:Oocytes / Q000254:growth & development; D011247:Pregnancy