The use of mineral oil during in vitro maturation, fertilization, and embryo culture does not impair the developmental competence of pig oocytes

Importance of oil overlay for production of porcine embryos in vitro

“…Another strategy is the creation of a microenvironment with elevated humidity around the incubation dishes through the addition of purified water in the central hole of a four‐well dish (Gasperin et al., ). Under these conditions, as reported for bovine embryo IVP (Gasperin et al., ), the osmolality values in the porcine IVM, IVF and IVC media through cultures were similar (~300 mOsm/kg) to those obtained in media covered with oil (Martinez et al., ). Therefore, this strategy can be used to maintain the osmolality of incubation media in the absence of an oil overlay.…”

“…Under these conditions, as reported for bovine embryo IVP (Gasperin et al, 2010), the osmolality values in the porcine IVM, IVF and IVC media through cultures were similar (~300 mOsm/kg) to those obtained in media covered with oil (Martinez et al, 2015). Therefore, this strategy can be used to maintain the osmolality of incubation media in the absence of an oil overlay.…”

“…Surprisingly, we observed that the IVM and IVF parameters were similar, regardless of the presence or absence of oil cover during incubations. However, embryo development (cleavage and blastocyst formation rates) was severely impaired when cultures were performed in the absence of an oil overlay (high osmolality), which confirms the harmful influence of inappropriate osmolality on gametes and/or embryos (Martinez et al, 2015).…”

“…Therefore, this strategy can be used to maintain the osmolality of incubation media in the absence of an oil overlay. The possibility of performing IVM, IVF and IVC within acceptable osmolality ranges, in the presence or absence of an oil overlay, permits investigations of the effects of oil overlay on oocyte and embryo development (Martinez et al., ). In this manner, and using comparable levels of culture medium osmolality, we have obtained similar rates of blastocyst formation with or without an oil overlay, which indicates that the oil overlay used was not harmful for the oocytes and embryos (Martinez et al., ).…”

“…Despite its importance, investigations evaluating the effects of MO on the osmolality of IVM/IVF/IVC media incubated under standard conditions (38.5°C, 5% CO 2 in air and 97% relative humidity) in IVP incubator units are very limited. We have recently shown that when the cultures are performed without an oil covering, the osmolality of the media is significantly increased compared to that obtained in the presence of oil overlay (Martinez et al, 2015). The increase was greater in IVF medium (from 295.5 to 445.5 mOsm/kg) than in IVM and IVC media (from ~298 to 310 mOsm/kg), which was probably due to the small IVF drop volume used (100 μl) compared to that used with the other media (500 μl).…”