Abstract
The present study was undertaken to examine whether the bovine nuclear transferred embryos produced by in vitro culture system could develop to young after transfer to recipients. Donor 8-to 16-cell stage embryos were obtained by in vitro maturation, in vitro fertilization and in vitro culture. Follicular oocytes maturated in vitro were used as recipient oocytes for nuclear transfer. Fusion of donor blastomere with recipient oocyte was induced by electric stimulation at 44 to 46 h of maturation. Of the 398 manipulated oocytes, 261 (66%) were fused with donor blastomere. Twenty-five (10%) embryos which developed into morula to blastocyst stage after co-culturing with cumulus cells in vitro. Fifteen embryos were transferred nonsurgically, 1 to 3 embryos per recipient, into the uterine horn of 9 heifers or cows on Day 7 to 9. The pregnancy rate was 44% (4/9) on Day 35 to 40. One recipient aborted on Day 60 to 70 and another on Day 50 to 60, respectively. Two normal offsprings were produced from the remaining 2 recipients. The production of calves for embryos transferred was thus low (13%). Nuclear transfer bovine em-bryos produced in vitro system developed to full-term.
