Estimates of pregnancy outcomes based on selection of bovine embryos produced in vivo or in vitro

摘要

Six evaluators graded day-7 embryos produced in vivo or in vitro (15 of each) by viewing video-recorded images of the embryos and classifying each for stage of development and quality (grades 1-4 excellent to degenerated on-transferable). Probabilities of pregnancy after embryo transfer were based on pregnancy rates of recipients at the facility of 1 evaluator where the percentages of heifers pregnant after transfer of grade 1, 2 and 3 embryos were 76, 65 and 54 respectively (in vivo), and 59, 45and 30 (in vitro). Within most grades, the proportion of embryos selected for transfer differed (P<0.05) among the 6 evaluators. Although no significant differences were found among evaluators in the proportion of recipients pregnant after transfer within any embryo grade, there was a substantial variation among evaluators in the proportion of recipients becoming pregnant, especially for in vitro-produced embryos. The pregnancy rates for grade 1, 2 or 3 in vivo-produced embryos were 66-76, 62-69 and 54-60% respectively, and the corresponding values for in vitro-produced embryos were 39-59, 15-45 and 24-32%. Approximately twice as many transfers were needed per pregnancy for in vitro-produced embryos as for those produced in vivo regardless of the grade.