02099naa a2200193 a 450000100080000000500110000800800410001910000110006024501550007126000090022652014770023565300110171265300100172365300120173365300130174565300130175865300120177177301220178310791902011-08-10       2010    bl uuuu     u00u1 u    #d1 aEpagri  aEffect of Fusion-Activation Interval and Embryo Aggregation on In Vitro and In Vivo Development of Cloned Bovine Embryos Produced by Handmade Cloning.  c2010  aDespite the rather success of cloning by somatic cell nuclear transfer (SCNT), the efficiency in development to term remains low, with a high rate of losses occurring throughout pregnancy due to faulty reprogramming and conceptus abnormalities. As the ideal fusion-activation interval for optimal nuclear reprogramming after cloning is still ill-defined, the aim of this study was to determine the effect of two distinct fusion-activation intervals and embryo aggregation on in vitro and in vivo development of clone bovine embryos. Increasing the fusion-activation interval to 4 h decreased cleavage but not blastocyst rates in 1 x 100% embryos. Blastocyst rates were lower in 1 x 100% embryos activated 2 h post-fusion. In general, cleavage and blastocyst rates for 2 x 100% embryos were higher than for 1 x 100% embryos (91.5% and 46.0% vs. 74.4% and 31.3%, respectively), irrespective of the activation time. Blastocyst rates for 4 hpf-activated embryos, based on cleavage, were higher than for 2 hpf-activated embryos (50.3% vs. 38.3%, respectively), despite the IVC scheme. Despite differences in in vitro development, pregnancy rates and conceptus development during the first two trimesters of pregnancy were similar between groups. A longer fusion-activation interval (4 hpf) or embryo aggregation scheme (2 x 100%) increased blastocyst yield but did not improve in vivo development nor pregnancy maintenance following the transfer to female recipients in cattle.  aBovine  aClone  aEmbryos  aHandmade  ain vitro  ain vivo  tIn: ANNUAL CONFERENCE OF IETS, 2010, Córdoba, Argentina. Proceedings... Sydney, Austrália: Csiro, 2010. p. 185-186.