Effects of seasonal changes on in vitro developmental competence of porcine oocytes.

The aim of this study was to investigate whether seasonal changes affected in vitro developmental competence of porcine oocytes. The relationship between atmospheric temperature and embryonic development of in vitro matured porcine oocytes following intracytoplasmic sperm injection was examined throughout the year. The blastocyst rate (31.1%) in winter (mean atmospheric temperature during December to February: -3.8 C) was significantly higher (P<0.05) than those of other seasons in 2008/2009 (19.7-23.5%; 6.3-17.5 C). The monthly mean blastocyst rates were negatively correlated with the temperatures (r=-0.5944, P<0.05). The results of the present study suggest that porcine embryos could be produced throughout the year, but the in vitro production efficiency was significantly affected by season, i.e., atmospheric temperatures. Furthermore, the results showed that winter is a favorable season for blastocyst production in the region of Obihiro, Hokkaido, Japan.