Development of Bovine Somatic Cell Nuclear Transfer Clones Constructed With Maternal (Autologous) Oocyte Cytoplasm (Ooplasts)

The objective of this study was to examine consequences of somatic cell nuclear transfer after fusion of somatic cell with maternal (autologous) or non-autologous ooplasts. To this end, granulosa cells from Jersey cows were fused with enucleated oocytes from the same Jersey cows (autologous ooplasts) or from Holstein, Hereford, and Angus cows (non-autologous ooplasts). The ability of cloned embryos to cleave and develop to morula or blastocyst was assessed on days 4 and 7 post-activation, respectively. Compact morulae and blastocysts were transferred to synchronized recipients and pregnancy confirmed by ultrasound 30-32 days post-estrus. Data were analyzed using Fisher's Exact Test. Development to the 8 to16-cell stage was greater for clones constructed with non-autologous ooplasts. However, morula and blastocyst development did not differ. Four pregnancies progressed beyond 200 days but fetal death occurred in three due to placental insufficiency. The one clone that progressed to term was constructed with a non-autologous ooplast, highlighting that the use of autologous ooplasm does not always improve somatic cell nuclear transfer outcomes.