Vitrification of in vitro cultured porcine two-to-four cell embryos

• The objective of this experiment was to evaluate the effect of a 5-day period of in vitro culture of two-to-four cell porcine embryos up to the blastocyst stage on their ability to survive vitrification and warming. In order to increase the cooling rate, superfine open pulled straws and Vit-Master (R) technology were used for vitrification. Two-to-four cell embryos were collected from weaned sows (n = 11) on day 2 (DO = onset of estrus). Some embryos (N = 63) were vitrified within 3 It after collection, warmed and cultured for 120 h (Group V2). Additionally, 81 two-to-four cell embryos were cultured for 96 It in order to obtain blastocysts; these were then vitrified, warmed and cultured for 24 h (Group VB; N = 65). The remaining two-to-four cell embryos were used as controls and thus not vitrified (control embryos; N = 70) but were cultured in vitro for 120 h. The V2, VB and control embryos were evaluated for their developmental progression and morphology during culture. All embryos (V2, VB and controls) were fixed on the same day of development in order to assess the total number of blastomeres. The survival and blastocyst formation rates obtained from V2 embryos were very poor (9.6 +/- 0.7% and 3.2 +/- 0.5%, respectively). The survival and hatching rates of VB embryos (75.0 +/- 0.69% and 33.6 +/- 0.13%) were lower (p less than 0.001) than those obtained with control embryos (89.1 +/- 0.8% and 47.5 +/- 0.12%). Hatched VB embryos had a lower (p less than 0.01) total cell number than hatched control embryos (70.3 +/- 4.5 versus 90.6 +/- 3.2, respectively). There was no difference between expanded VB and control blastocysts. In conclusion, blastocysts derived from in vitro culture of two-to-four cell pig embryos could be successfully vitrified using SOPS straws and Vit-Master (R). (c) 2007 Elsevier Inc. All rights reserved.

Nyckelord

porcine; embryo; vitrification; two-to-four cell

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