Liquid storage of porcine in vitro -produced blastocysts; a practical approach for short storage.

Commercial application of embryo transfer in pig breeding is dependent on the storage of embryos. The aim of this study was to assess the embryo quality of in vitro -produced blastocysts after 3 h liquid storage at 37°C in CO 2 -free medium by evaluating morphology, in vitro developmental capacity and apoptosis. Blastocysts at days 5 and 6 post-fertilization were randomly allocated to the storage group (HEPES-buffered NCSU-23 medium including bovine serum albumin in a portable embryo transport incubator at 37°C) or a control group (porcine blastocyst medium in a conventional culture incubator). Thereafter, blastocysts were evaluated for morphology and stained to assess apoptosis straight after the 3 h storage period or after a further 24 h conventional incubation. There was no significant difference between the storage and control group after 3 h storage and the further 24 h conventional incubation for any of the parameters, nor for apoptosis straight after the 3 h storage. Embryos that reached the blastocyst stage at day 5 showed less apoptosis (6.6% vs 10.9%, P = 0.01) and a trend for a higher rate of developmental capacity (70.6% vs 51.5%, P = 0.089) than embryos reaching the blastocyst stage on day 6. In conclusion, in vitro -produced porcine blastocysts can be stored for 3 h at physiological temperature in transportable incubators using a CO 2 -independent medium without compromising quality.