“…Ultraviolet (UV) irradiation and excitable DNA‐specific dyes such as Hoechst 33342 (H342) have often been used to aid the visualization of the nuclear material and the polar body before enucleation (Estrada et al, 2008; Lee et al, 2008; Hickey et al, 2011) or to confirm the enucleation of recipient oocytes after manipulation (Kragh et al, 2005; Das et al, 2010; Koo et al, 2010; Biswas et al, 2011). Exposure of the recipient oocytes to H342 and UV irradiation, however, may be detrimental for oocyte developmental competence, as reported for several species including cattle (Smith, 1993; Dominko et al, 2000), goat (Velilla et al, 2002), rabbits (Yang et al, 1990), and mice (Versieren et al, 2010). We have recently demonstrated that the exposure of oocytes to H342 and UV irradiation has a deleterious effect on the development of in vitro‐fertilized porcine oocytes, with increasing exposure to UV irradiation (up to 30 sec) producing more drastic effects (Maside et al, 2011).…”