[In vitro dissection and development of sheep embryos after preservation at very low temperature (-196 degrees C)].

Embryos obtained from Sardinian breed ewes superovulated with FSH-p (Sigma) were frozen at -196 degrees C in liquid nitrogen. After 6 months storage, the embryos (12, all at the compact morula stage), were thawed in a water bath at 39 degrees C for 30 minutes. Six embryos were dissected with a Leitz micromanipulator using a simplified technique. Both demi and intact embryos, were cultured in medium TCM 199 + 10% FCS at 38 degrees C in 5% CO2 for 24 hours. Only five demi-embryos (41.6%) became blastocysts versus 4 whole embryos (66.6%) after the culture period. Splitting as our results show, lowers the embryo viability after freezing-thawing, but it can be used in certain instances to obtain genetic improvement in the Sardinian breed.