While undifferentiated cells (at least in mice) may have a higher capacity to produce term development after SCNT, there is no true embryonic stem cell currently available for pigs. While
there is not a verified ES cell in pigs, recent reports on the development of induced pluripotent cells in pigs may provide stem cells for NT. In light of the absence of an ES cell in the pig, different types of adult stem cells have been tested to mprove the efficiency of NT in pigs. For example, mesenchymal stem cells were successfully used for NT, and these clones showed higher blastocyst formation and lower incidence of apoptosis when compared to embryos derived from fetal fibroblast cells. Moreover, similar results were reported when skin-derived stem cells were used for NT. Finally, SCNT embryos derived from salivary gland-derived progenitor cells had increased in vitro developmental potential compared to embryos from fetal fibroblast cells, and they produced live piglets.