In vitro fertilization (IVF) in straws and a short gamete coincubation time improves the efficiency of porcine IVF.

The present study was designed to evaluate three different in vitro fertilization (IVF) systems: a straw-IVF system with 10 min of coincubation, a straw-IVF system with 6-h coincubation and the microdrop-IVF system with 6-h coincubation (the traditional IVF system used routinely in most of IVF laboratories) in an attempt to reduce polyspermic penetration (Experiment 1). When the straw-IVF system was tested in combination with two coincubation times, the use of 10 min of coincubation significantly increased (p < 0.001) the penetration rate and the efficiency of fertilization (67.7 +/- 6.4% vs 31.9 +/- 6.5% and 41.5 +/- 2.5% vs 17.6 +/- 2.5% for 10 min and 6 h, respectively), while there were no significant differences in the incidence of monospermy between both systems (64.3 +/- 5.1% and 67.7 +/- 3.4%, for 10 min and 6 h, respectively). The penetration rate in the 6-h microdrop-IVF system was higher (93.8 +/- 3.6%; p < 0.001) compared with the 10-min straw-IVF system (67.7 +/- 6.4%), however, monospermy was severely reduced (25.0 +/- 4.3% vs 67.7 +/- 3.4%, for the 6-h microdrop-IVF system and 10-min straw-IVF system, respectively). The efficiency of the IVF showed similar values between microdrop and 6-h straw-IVF systems, but efficiency was significantly improved (p < 0.05) when the 10-min straw-IVF system was used. Experiment 2 was designed to compare porcine in vitro embryo production in two IVF systems, the 6-h microdrop-IVF system (1000 sperm per oocyte) and 10-min straw-IVF system (30 000 sperm per oocyte). The blastocyst formation rates tended (p = 0.06) to be higher when the 10-min straw-IVF system was used compared with the 6-h microdrop-IVF system. In addition, the number of total cells per blastocyst increased significantly (p < 0.05) in the 10-min straw-IVF system. These results showed that the 10-min straw-IVF system is an effective way to decrease polyspermic penetration, and improve the efficiency of fertilization and the quality of blastocysts in terms of cell number per embryo.