Cloned Calves Produced by Transfer of Reconstituted Embryos Derived from Fibroblast Cells of a Female Fetus

Abstract

The viability of reconstituted embryos derived from bovine somatic cells were evaluated. A total of 54 fetal somatic cell-derived embryos, in which some embryos were previously cryopreserved, were transferred to 12 recipient cattle (total 26 times). Three of 12 cattle that received fresh embryos became pregnant and delivered 3 calves (1 aborted at 223d and 2 live born), whereas none out of the 5 recipients became pregnant after transfer of embryos cryopreserved by slow cooling. Of 9 cattle that received embryos vitrificated 2 became pregnant. One of these two vitrification-derived embryos died during early pregnancy and another developed to term but was stillborn. These aborted fetuses, stillborn calf and two live born calves were identified as being derived from donor cells. The growth of live born calves showed no abnormalities when examined at 8 months of age. It was therefore concluded that: reconstituted embryos derived from fibroblast cells from female fetus could develop to term, that vitrification might be available to preserve these embryos and that transfer of these fresh embryos resulted in viable offspring with normal growth.