Differences in sperm migration through cervical mucus in vitro relates to sperm colonization of the oviduct and fertilizing ability in goats

Abstract

Sperm migration in estrous cervical mucus can be used to measure the ability of spermatozoa to migrate through the genital tract. The relationship of this test with the sperm colonization of the isthmus, and its impact on fertility has not been evaluated in goats. Our objectives were to determine the differences among spermatozoa of different bucks in their ability to penetrate homologous cervical mucus in vitro and to determine the relationship between sperm displacement through cervical mucus and the ability of spermatozoa to colonize the oviduct and penetrate IVM oocytes, in vivo. Sperm migration in cervical mucus was assessed in flat capillary tubes with a phase contrast microscope. In the first experiment, fresh semen was used to establish differences between males in the ability of their spermatozoa to migrate in cervical mucus. In the second experiment, goats in estrus were inseminated with fresh spermatozoa from males with significant differences in mucus migration ability, and sperm numbers were evaluated at the UTJ. In the third experiment, the fertilization efficiency of IVM oocytes transferred to the oviduct of estrous females inseminated with semen from the same males as earlier, was used to assess the relationship between the mucus migration test and the in vivo fertilization performance of their spermatozoa. Spermatozoa from different males varies significantly in sperm migration efficiency in cervical mucus (15.5 a±1.2; 14.9 a±1.4; 17.5 ab±1.2; 17.0 ab±1.5; 19.7 b±1.2; 20.1 b±1.4 mm; media±S.E.M. for males A–F, respectively, P<0.05). Spermatozoa from males with different mucus migration efficiency values produced different sperm populations at the oviduct reservoir of inseminated females (1233±92.3 versus 28.8±17.0 spermatozoa of males with high and low relative migration efficiency, respectively, P<0.02). Spermatozoa from males with different mucus migration efficiency values have different fertilization rates of IVM oocytes transferred to oviduct (47/96 (49.0%) versus 25/91 (27.5%) for males with high and low relative migration efficiency, respectively, P<0.05). Cumulative results suggest that sperm migration in cervical mucus is related to the ability of spermatozoa to colonize the oviduct and to fertilize matured oocytes in vivo.