Concentrations of spermatozoa in the vagina of heifers after deposition of semen in the uterine horns, uterine body or cervix

Summary.In Exp. I, virgin Holstein heifers (N = 18) were induced into oestrus with PGF-2α. Animals which stood to be mounted were paired for insemination ∼8 h later with 56·1 × 106spermatozoa from a single bull. Semen was deposited in the uterine body of one female. Each matched female was inseminated by deposition of one-half of the inseminate into the right uterine horn and one-half into the left uterine horn ∼ 7·0 cm anterior to the internal cervical os. In Exp. II, additional heifers (N = 18) were induced into oestrus and inseminated by deposition into the uterine horns or cervix (2·0 cm anterior to the external cervical os). A 1·0 ml aspirate of vaginal mucus was collected at hourly intervals for 8 h after insemination. Concentration of spermatozoa was determined by haemocytometry. In Exp. I, cumulative percentage spermatozoa recovered in an 8 h collection period were similar (P> 0·10) for insemination into the uterine horns (17·9 ± 2·9%) and uterine body (18·5 ± 4·5%). In Exp. II, cumulative % sperm recovery from the vagina was greater (P< 0·10) for cervical deposition (59-1 ± 14·1%) than for that into the uterine horns (30·9 ± 7·8%). In Exp. II, the insemination treatment × hour of sample interaction was significant (P< 0·08). Recovery of spermatozoa from the vagina was greatest (P< 0·05) within 3 h after cervical insemination (31 ·4 ± 9·9% compared to 9·4 ± 2·5% for uterine horn deposition). Percentage recovery of spermatozoa from the remaining hourly collections were similar (P> 0·10). These results suggest that retrograde movement of spermatozoa from the uterus to the vagina was similar after insemination into the uterine horns or uterine body and 2-fold greater after cervical deposition.Keywords:cattle; insemination site; sperm loss