Oviductal Fluid Supplementation during Maturation and Fertilization Improves in Vitro Embryonic Development in Pigs

Oviductal fluid has a major role in the maturation of gametes and the process of fertilization. The objective of this study was to determine the effects of oviductal fluid supplementation in vitro, during oocyte maturation and in vitro fertilization (IVF) on oocyte maturation, spermatozoa and fertilization characteristics, and early embryonic development rates. During the last 24 h of maturation, oocytes (n=1423) were placed into maturation media supplemented either 1% (v/v) or 5% (v/v) thawed snap-frozen oviductal fluid. Fertilization was performed using pooled frozen-thawed semen from three different boars. During IVF, the fertilization media was supplemented with 1%, (v/v) or 5% (v/v) oviductal fluid. At the end of maturation oocytes (n = 195) were evaluated for intracellular glutathione (GSH) levels, GSH peroxidase activity and nuclear maturation. Fertilization characteristics were evaluated 12 h after IVF and rates of embryonic cleavage and blastocyst development were observed at 48 h and 144 h after IVF, respectively. Sperm were evaluated for forward progressive motility, viability, and the ability to undergo the acrosome reaction (capacitation) at 0, 2, 4, 6 h after thawing. There were no significant differences in the percentages of oocytes that reached metaphase II by the end of maturation, GSH peroxidase activity, forward progressive motility, ability to undergo the acrosome reaction, or sperm penetration rates after IVF. Supplementation with 1% (v/v) oviductal fluid had significantly higher (P < 0.05) GSH concentration levels in oocytes and higher viable sperm at 2 h post thaw. Oocytes treated with 1% (v/v) oviductal fluid during the end of maturation and IVF (33.33 ± 2.61) and 5% (v/v) oviductal fluid during maturation (33.33 ± 2.66) or IVF (39.53 ± 3.78) had significantly less (P < 0.05) incidence of polyspermic penetrations and a significantly higher (P < 0.05) incidence of male pronuclear formation (87.50 ± 4.01; 86.67 ± 4.83; 86.05 ± 3.19, respectively) compared to no oviductal fluid supplementation. Oocytes supplemented with 5% (v/v) oviductal fluid during maturation and IVF had significantly lower (P < 0.05) incidences of polyspermic penetration (27.91 ± 2.50) and significantly higher (P < 0.05) percentages of embryos reaching the 2 cell stage (81.76 ± 3.72) and blastocyst stage of development (37.74 ± 1.09) by 48 and 144 h, respectively, compared to all other groups. The results of this study suggest that supplementing 1% and 5% (v/v) oviductal fluid during maturation and IVF improves the success rates of in vitro embryo development in pigs.