Sperm migration in pigs after deep intrauterine and intraperitoneal insemination

Deep intrauterine insemination in pigs allows sperm deposition only into one uterine horn, but bilateral fertilization of oocytes occurs. How the sperm reach the contralateral oviduct remains disputable. The aim of this experiment was to study possible transperitoneal and/or transuterine sperm migration ways. Follicle growth and ovulation were induced in 24 peripubertal gilts with eCG and hCG 72 h after eCG. Endoscopic intrauterine insemination (IUI) was performed 32 h after hCG with 20 ml of extended semen (60 × 10(6) spermatozoa) as follows: Group CONTROL (n=8) received IUI into the right horn, and the left horn served as non-treated control; Group LIGATURE (n=8) received IUI into the right horn, and the left horn was closed by endoscopic double ligature close to the bifurcation; Group INTRAPERITONEAL (IPI; n=8) received IUI into the right uterine horn, the left horn was closed by double ligature and semen was deposited intraperitoneally at the surface of the left ovary. Genital tracts were removed 65-66 h after hCG, the oviducts were flushed and ova (n=299) were analyzed for fertilization and cleavage. Furthermore, the accessory spermatozoa count/oocyte was graded as 0, without spermatozoa, 1, <5 spermatozoa, 2, 5-50 spermatozoa, 3, 50-100 spermatozoa and 4, >100 spermatozoa. The results indicate that low dose IUI into one horn provides a lower grade of accessory spermatozoa in the contra-lateral side (1.6 vs. 2.8). No spermatozoa were found in ova flushed from oviducts of the ligated uterine horn, even after intraperitoneal insemination (P<0.05), and no fertilization occurred, respectively. Our results clearly indicate that after low dose IUI into one uterine horn, spermatozoa reach the contralateral oviduct via transuterine migration.