A retrospective clinical study of endoscopic-assisted transcervical insemination in the bitch with frozen–thawed dog semen
Since the conclusion of data collation from previously published work, a further 352 inseminations using frozen–thawed dog semen by endoscopic-assisted transcervical insemination (EIU) have been performed by the author. Insemination was performed on the second day in which crenulation of the anterior vagina was detected in conjunction with a progesterone concentration of >10 ng/ml. All semen samples were analysed for total number of sperm, total motility and progressive motility using computer-assisted semen analysis (CASA). The insemination dose was based on the progressively motile normal spermatozoa (PMNS). Insemination was performed on all bitches as previously described using a ureterorenoscope. Additional extender was inseminated subsequent to the semen to expand and fill the uterus. The semen and additional extender were inseminated slowly over a period of 15–20 min. Pregnancy was determined by B-mode ultrasound equipped with a 7.5-MHz probe whilst standing and/or via the whelping rate. The number of sperm inseminated ranged from 9 × 106 PMNS to 519 × 106 PMNS, with progressive motility values ranging between 20% and 80%. The overall pregnancy rate was 68% (238/352). When stratified by PMNS, pregnancy rates were as follows: >150 × 106 PMNS - 76% (110/145), 100–150 × 106 - 68% (87/128) and <100 × 106 PMNS - 52% (41/79). Pregnancy rate was significantly higher when >150 × 106 PMNS (p = .003) or 100–150 ×106 PMNS (p = .027) were inseminated compared to <100 × 106 PMNS. These data are concordant with previous reports recommending the insemination of >150 × 106 PMNS to maximize pregnancy rate. These results indicate that one optimally timed EIU insemination results in similar pregnancy rates to previous publications of one optimally timed, or two or more non-optimally timed inseminations using the Norwegian catheter.