Abstract
This study aimed at increasing the efficiency of current protocols for the production of live piglets from cryopreserved embryos. Porcine early hatched blastocysts (n=163) were cryopreserved in liquid nitrogen in the presence of 1.5 M glycerol (1.5G), 1.5 M glycerol + 0.25 M sucrose (GS) or 1.8 M glycerol (1.8 G) using a conventional slow cooling method, and their post-thaw survival assessed following in vitro culture or transfer. Post-thaw survival rates of embryos were 85.1%, 91.6% and 94.1% in 1.5 G, 1.8 G and GS groups, respectively. More embryos which maintained prefreeze morphology were obtained in GS (41.7 %, P<0.001) and 1.8 G groups (29.1%, P<0.025) compared with 1.5 G group (10.0%). Transfer of 171 frozen-thawed embryos from the three groups after culture for 24 h to 4 recipients did not result in pregnancy. In contrast, transfer of 66 embryos from GS group to a recipient 3 h after thawing resulted in the birth of 4 piglets. The results demonstrate that addition of 0.25 M sucrose to the freezing media improves post-thaw survival compared with freezing with glycerol alone.
