Sperm distribution in the genital tract of the bitch following artificial insemination in relation to the time of ovulation

In the present study, sperm distribution in the genital tract of the bitch following artificial insemination (Al) in relation to the time of ovulation was investigated by histology, scanning electron microscopy (SEM) and flushing. Ten bitches were inseminated intravaginally with 500 x 10 6 spermatozoa: three dogs before ovulation, four dogs during ovulation and three dogs after ovulation. Ovariohysterectomy was performed 24 h after Al. Half of the genital tract was divided into nine segments (cervix, corpus uteri, caudal, middle and cranial uterine horn (UTH), utero-tubal junction (UTJ), isthmus, ampulla and infundibulum), which were processed for histology and SEM. The contralateral UTH and uterine tube (UT) were flushed, and several sperm characteristics were assessed. Histology revealed that the spermatozoa were mainly located in the uterine glands and at the UTJ, while very few spermatozoa were detected in the UT. Insemination during ovulation resulted in higher percentages of glands with spermatozoa in the different parts of the uterus (P < 0.05). Evaluation by SEM showed higher numbers of spermatozoa in several parts of the uterus for bitches inseminated during ovulation (P < 0.05). The mean number of spermatozoa flushed from the UTH and the UT was low. No significant differences in the evaluated sperm quality parameters were found between the flushings of the UTH and the UT. In conclusion, based on our findings, the uterine glands and the UTJ might act as sperm reservoirs in the bitch and sperm transport in the genital tract is affected by the time of Al in relation to ovulation.