Abstract
The purpose of this study was to examine the suvival rates of cryopreserved porcine embryos collected on Day 6 (Day 0=onset of estrus) with various cryprotectants. Eighty two embryos at different stages, ranged from expanded blastocyst to hatched blastocyst, were allocated to 6 experimental groups in different combinations of cryoprotectants glycerol, egg yolk and/or trehalose. Porcine embryos were cryopreserved using conventinal slow freezing precedures. The embryos were equilibrated with one of the freezing solutions, cooled from 25 to -7$^{\circ}C$ at 1$^{\circ}C$/min, seeded at -7$^{\circ}C$ frozen to -36$^{\circ}C$ at 0.5$^{\circ}C$/min, and then plunged into liquid nitrogen. The frozen embryos were thawed by immersion in 37$^{\circ}C$ water and the cryoprotectants were removed by dilution with 0.5M sucrose solution. Embryonic survival was estimated from the normal development of embryos for 12, 24 and 48hrs culture. Then the embryos were stained and their cell nuclei was counted. The survival rates of morphological embryos were significantly higher in group I (10% glycerol) or group IV (10% glycerol＋10% egg yolk＋0.5M trehalose) than those in other groups, although the nuclei number was quite higher in embryos treated with 10% glycerol and 0.25M trehalose at expended blastocyst. However, hatched blastocysts showed higher viability and nuclei number treated with either egg york or trehalose, but the survival rates after 48hrs of culture were quite low. These results indicate that egg yolk and trehalos as a supplement to freezing solutions can be useful to the cryopreservation ofn porcine embryos.
