Development of Porcine Embryos from One- and Two-Cell Stages to Blastocysts in Culture Medium Supplemented with Porcine Oviductal Fluid1

Oviductal fluid (OVF) was harvested chronically from 5 sows beginning on Day 1 of the estrous cycle (Day 0 of estrous cycle = day of detected estrus) and used for embryo culture (Day 3 OVF only). Two experiments were conducted to investigate in vitro development of 1-cell and 2-cell porcine embryos in a modified Kreb's Ringer bicarbonate medium (culture medium, CM), early luteal phase OVF or CM supplemented with OVF (CM-OVF, 25% OVF v/v in CM) with or without transfer to fresh CM. In Experiment 1, 1-cell and 2-cell embryos were harvested from sows (n = 7) approximately 44 h after detected estrus. In Experiment 2, 1-cell embryos were collected from 5 sows treated with altrenogest and gonadotropins, approximately 50 h after injection of human chorionic gonadotropin. The volume of OVF (ml) declined progressively throughout the 4 days of collection (24 h, 8.44 ± 0.28; 48 h, 6.88 ± 1.78; 72 h, 4.96 ± 0.35; 96 h, 4.64 ± 0.25 after onset of estrus; p < .01). In both experiments, development to blastocyst stage was lowest among embryos cultured in OVF and highest among those cultured in CM-OVF (Experiment 1: CM, 27.3; OVF, 10; CM-OVF, 63.6; Experiment 2: CM, 26.7; OVF, 0; CM-OVF, 82.4; % blastocyst formation). When embryos exposed to OVF and CM-OVF for 48 h (1-cell embryos) or 24 h (2-cell embryos) were transferred to fresh CM, development to blastocyst stage improved (CM to CM, 27.3; OVF to CM, 58.3; CM-OVF to CM, 100; % blastocyst formation) in Experiment I. In Experiment 2, only embryos transferred from OVF to fresh CM showed improvement in percentage blastocyst formation (CM to CM, 29.3; OVF to CM, 35.3; CM-OVF to CM, 77.8). This study indicates that addition of OVF to culture medium results in improved development in vitro of porcine embryos from 1-cell to blastocyst. Early luteal phase porcine OVF by itself inhibits the development of 1-cell and 2-cell porcine embryos in vitro.