Distribution of Spermatozoa in the Reproductive Tracts of Sows after Intra-uterine Insemination Using Frozen-thawed Boar Semen

The aims of the present study were to determine the number of spermatozoa in the reproductive tract of sows after intra-uterine insemination (IUI) with frozen-thawed (FT) boar semen and to investigate the influence of adding seminal plasma in the thawing medium on the sperm transport in the female reproductive tract. Fourteen multiparous sows were divided into 3 groups: group I (n= 5), insemination with 80 ml of extended fresh semen, group II (n= 4), insemination with 40 ml of FT semen diluted with ModenaTM extender and group III (n= 5), insemination with 40 ml of FT semen diluted with combination of ModenaTM and seminal plasma. All the sows were inseminated once with 2x109 motile spermatozoa at 36.1±2.8 hours after human Chorionic Gonadotropin (hCG) administration. The reproductive tract was collected from the sows at 12.4±2.2 hours after insemination and was divided into 5 parts, i.e. ampulla, cranial isthmus, caudal isthmus, utero-tubal junction (UTJ) and cranial uterine horn. All parts of the reproductive tract were flushed by phosphate buffer solution and the number of spermatozoa was determined using a Neubauer hemocytometer. Spermatozoa were found in all parts of the sows’ reproductive tracts at 12.4 hr after IUI using either fresh (group I) or FT boar semen (group II and III). Most of the spermatozoa were found in the UTJ (47.8%, 47.8% and 38.1% in group I, II and III, respectively, p> 0.05) and the caudal isthmus (27.2%, 26.4% and 28.1% in group I, II and III, respectively, p> 0.05). The total number of recovered spermatozoa in group III (409,420 sperm) tended to be higher than group I (286,750 sperm, p= 0.109) and II (287,000 sperm, p= 0.139). Number of spermatozoa in the cranial isthmus in group III (76,400 sperm) tended to be higher than that in group I (35,750 sperm) and II (33,333 sperm) (p> 0.05). It can be concluded that at 12.4 hr after IUI using FT semen, spermatozoa were found in all parts of the reproductive tracts of the sows similar to that using extended fresh semen. Supplementation of seminal plasma in the thawing medium of FT boar semen tended to increase the transportation of spermatozoa toward the cranial isthmus. This might be due to the suppression of PMN cells in the female reproductive tract and the reduction in cryoinjury of the FT boar sperm caused by seminal plasma.