Our goal was to examine the effects of early denudation on the enucleation efficiency and developmental competence of embryos following somatic cell nuclear transfer (SCNT) and parthenogenetic activation (PA). Oocytes were denuded following 30 h of in vitro maturation (IVM) and then cultured with (D+) or without (D-) their detached cumulus cells for additional h. Control oocytes were denuded after h of IVM. The size of the perivitelline space was larger at 40 h of IVM () than at 30 h ( p<0.01). The distances between the metaphase II (M II) plates and the polar bodies (PBs) were shorter in D+ () and D- oocytes () than in control oocytes ( p<0.01). Enucleation rates following blind aspiration at 40 h of IVM were higher (p<0.01) in D+ (92%) and D- oocytes (93%) compared to controls (82%). Early denudation did not affect oocyte maturation or the in vitro development of SCNT and PA embryos. When SCNT embryos from D+ oocytes were transferred to four gilts, pregnancy was established in two pigs, and one of them farrowed three live piglets. In conclusion, early denudation of oocytes at 30 h of IVM could improve the enucleation efficiency by maintaining the M II plate and the PB within close proximity and support the in vivo development of SCNT embryos to term.

• Song, Kil-Young
• Hyun, Sang-Hwan
• Lee, Eun-Song