Effect of chilling on the development of in vitro produced bovine embryos at various cleavage stages.
OBJECTIVE
Bovine embryos and zygotes are known to be sensitive to "temperature shock" when cooled to temperatures near 0 degrees Celsius. The effect of chilling on in vitro derived embryos at various cleavage stages was investigated.


METHODS
Cumulus-oocyte-complexes (COCs) were matured in IVM medium with serum. Presumptive zygotes were cultured in serum free in vitro culture (IVC) medium. Embryos were used as chilled or control samples at the 2-cell, 4-cell, 8-cell, morula, and blastocyst stages. Embryos in 0.2 mL PBS in plastic straws were cooled rapidly in ethanol baths at 0 degrees Celsius for 30 min. Embryo viability was assessed by in vitro development.


RESULTS
The percentage of control embryos that hatched as blastocysts increased the later stage at which they were selected. Relative proportion of embryos increased from 28% to 48% to 68% when chilled at the 8-cell, morula or blastocyst stages.


CONCLUSIONS
IVF-produced embryos are differentially susceptible to cooling injury. Cell counts made of those blastocysts formed from chilled embryos indicated subtle effects of chilling.
Balasubramanian
S
S
Department of Animal Reproduction, Gynaecology and Obstetrics, Madras Veterinary College, Tamil Nadu Veterinary and Animal Sciences University, Chennai, 600 007, Tamil Nadu, India.
Rho
Gyu-Jin
GJ
D000818:Animals; D002417:Cattle; D002970:Cleavage Stage, Ovum; D015925:Cryopreservation; D005260:Female; D008297:Male; D014022:Tissue Survival