Abstract:
The effect of embryo age on development and ratio of live : dead cells aftervitrication and warming was examined. One-step and three-step addition ofcryoprotectants in vitrification solution (40% ethylene glycol,0·3 M trehalose and 12% polyvinylpyrrolidone) were comparedusingin vitro produced (IVP) bovine blastocysts andexpanded blastocysts. Rates of development and hatching were 74·2% and 41· 9% for Day 7, 57·8% and23· 8% for Day 8, 33· 7% and 6·1%for Day 9 embryos with one-step addition. In three-step addition, those rateswere 86·2% and 77·3% for Day 7,72·3% and 39·0% for Day 8, 47·3% and10·5% for Day 9 embryos. Day 7 embryos showed highest(P < 0·01) development and hatching rates withone exception. Hatching rate of Day 7 embryos with three-step addition washigher (P < 0·01) than with one-step addition.The ratio of live : dead cells differed between one-step (94%) andthree-step (97%) additions for Day 7 embryos (P < 0· 05). Theresults indicate the higher resistance of younger IVP bovine embryos againstvitrication and the potential for three-step addition of cryoprotectants toyield a higher survival rate after warming than with one-step addition.