SURVIVAL AND VIABILITY OF FRESH AND FROZEN-THAWED IN-VITRO BOVINE BLASTOCYSTS

Three experiments were undertaken to investigate the effect of some fa ctors on survival and viability of bovine blastocysts produced in vitr o in serum-free oviduct-conditioned media. In vitro survival to freezi ng was higher for blastocysts appearing on days 6 and 7 than for day 8 blastocysts (67 and 50% hatching rate vs 12%). Transfer success of da y 8 blastocysts to recipient heifers was 35% (9/26) carves born vs 19% (4/21) for cows. Embryo mortality occurred mainly during the periimpl antation period (between days 21 and 45) for cows compared with heifer s. Calving rate-after direct transfer of frozen blastocysts without di lution was 24% (4/17) compared with 31% (5/16) for control unfrozen bl astocysts.