THE EFFECT OF VITRIFICATION DEVICE AND EMBRYONIC STAGE ON SURVIVAL AND DEVELOPMENTAL COMPETENCE OF GABALI RABBIT EMBRYOS

Abstract

the current study aimed to evaluate the effect of vitrification device (straw or cryotop) and embryonic stage (4-8 cell or morula stages) on survivability, normality and in vitro embryo development rate into blastocysts/hatched blastocysts. Total of 24 mature rabbit does of Gabali breed (5-6 months of age, 3-3.5 kg live body weight) were used in this study as embryo donors. Rabbit does were superovulated by PMSG and hCG. Embryos at 4-8 cell stage were recovered by flushing oviducts 32–43h post-mating, while, embryos at morula stage were recovered by flushing oviducts 64-66 h post-mating. Embryos were vitrified by straw or cryotop. Survival and normality rates were determined. The vitrified embryos were in vitro cultured for 3-5 days to record blastocyst and hatching blastocyst formation rates. Results showed insignificant differences in survival and normality rates of vitrified embryos as affected by embryonic stage, although there were a tendency of higher rates yielded from embryos at morula than at 4-8 cell stage (87.7 and 89.2% vs. 85.9 and 85.2%, respectively). Survival and normality rates were higher (P<0.05) using cryotop than straw, being 92.1 and 93.1% using cryotop versus 81.7 and 81.0% using straw, respectively. Expansion and hatching rates were higher (P<0.05) for vitrified embryos at morula than at 4-8cell stage (80.0 and 71.5% vs. 66.0 and 54.0%, respectively) and using cryotop than straw (81.6 and 75.3 vs. 63.1 and 48.2%, respectively).The current study could be conclude that using the cryotop method to vitrify rabbit embryos rather than straw method at various developmental stages, particulary at morula stage.