Distribution of spermatozoa in the genital tract of artificially inseminated heifers.

Eight heifers were artificially inseminated in the uterine body with 160×10 spermatozoa frozen in French mini-straws. The heifers were slaughtered 2 (n = 4) or 12 (n = 4) h after insemination and spermatozoa were recovered by flushing defined segments of the reproductive tract. The efficiency of the method was checked in different ways. There was a slight underestimation of the number of recovered spermatozoa. This underestimation was randomly distributed among heifers and genital tract segments. The total number of spermatozoa recovered was higher at 2 than at 12 h (14.6 vs 0.6 % of the total number inseminated). Most spermatozoa were found in the vagina both at 2 and 12 h after insemination and in greater number at 2 h. In uterus there was a slight decline in the number of spermatozoa recovered at 2 versus 12 h after insemination. The number of spermatozoa recovered from the oviducts were similar at 2 (89.6 × 10) and 12 h (71.5 × 10) after insemination. At 2 h spermatozoa were found in all parts of the oviduct with the majority located in the utero tubal junction, whereas at 12 h the most were recovered from isthmus. More spermatozoa were recovered from the left than from the right side of the tract in 6 of the 8 heifers. Only in 1 heifer were the majority of spermatozoa found in the oviduct ipsilateral to the follicle bearing ovary.