Development of Early Porcine Embryos In Vitro and In Vivo1

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Abstract
In vitro development of early porcine embryos under different culture conditions was evaluated and compared to in vivo development. First, one- and two-cell embryos were collected and cultured individually in 20-μl drops under 5% CO2 in air for 4 days. Embryos from one oviduct were cultured in NCSU-23, and those from the contralateral oviduct were cultured in KSOM/AA. The embryos developed in NCSU-23 had a higher mean number of inner cell mass (ICM) nuclei compared to those developed in KSOM/AA (p = 0.025). They also had higher trophectoderm (TE) and total nuclear number (p = 0.001), while there was no difference in the average ratio of ICM to TE nuclei (p = 0.731). When the effect of different gas atmospheres was tested, the numbers of TE and total nuclei were higher (p < 0.01 and p < 0.025, respectively) in embryos cultured in an atmosphere with 5% CO2 in air than in those developed under 5% CO2:5% O2:90% N2. Next the development of embryos cultured in NCSU-23 was compared to that of embryos incubated in vivo. By the end of the 4-day incubation, the cultured embryos had higher nuclear numbers and a higher ratio of ICM to TE nuclei than those developed in vivo (p < 0.001). Finally, the embryos that developed in NCSU-23 or in vivo were transferred into recipients. By Day 40 of pregnancy, 37.1 ± 15.3% of the in vitro- and 53.8 ± 15.3% of the in vivo-incubated embryos formed conceptuses. These results indicate that despite the lower nuclear numbers caused by in vitro conditions, the cultured embryos were developmentally competent.
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