Effects of porcine follicular fluid and oviduct-conditioned media on maturation and fertilization of porcine oocytes in vitro.

Advances in porcine in vitro fertilization have been impaired by low normal fertilization rates resulting from a high rate of polyspermy. The present study was undertaken to determine the effects of porcine follicular fluid (pFF) and oviductal explant-conditioned medium on maturation and fertilization of porcine oocytes in vitro. Oocytes and pFF were collected from small, medium, and large follicles and pooled within size category. Maturation and fertilization media were supplemented (10%) with either fetal calf serum (FCS) or pFF (either fresh or snap-frozen). Snap-frozen pFF from small (3.1-5.0 mm) and medium (5.1-7 mm) follicles, respectively, increased maturation rates of oocytes from small and medium follicles by nearly 36% (p < 0.05) compared with those treated with FCS or fresh pFF. Supplementing media with either fresh or snap-frozen pFF from medium follicles reduced (p < 0.05) polyspermy of oocytes from small follicles by 30% compared with supplemental FCS. Snap-frozen pFF increased (p < 0.05) normal fertilization compared to that in fresh pFF (29% vs. 18%). Supplementing oocytes from medium follicles with snap-frozen pFF yielded the lowest (18%, p < 0.05) polyspermy rate. Oocytes from both small and medium follicles supplemented with pFF and/or conditioned medium (CM) from oviducts of periovulatory gilts exhibited a 95% improvement in normal fertilization rate and a 34% decrease in polyspermy rate compared to those treated with FCS (p < 0.05). CM from oviducts of luteal gilts did not improve rates of polyspermy and normal fertilization (p > 0.05). We conclude that snap-frozen follicular fluid from medium follicles and CM from cultured oviducts of periovulatory gilts improve in vitro maturation, reduce polyspermy, and increase normal fertilization rates in vitro.