Vaginal impedometry for detection of optimal breeding time in bitches.

OBJECTIVE: To compare the efficacy of canine vaginal impedometry in identifying the preovulatory luteinizing hormone (LH) peak to that of currently used methods (serum progesterone concentration measurement, vaginal cytologic evaluation, and vaginoscopy).

DESIGN: Prospective study.

ANIMALS: 12 sexually intact female dogs.

PROCEDURES: 12 mature postpubertal Beagle (n = 3), Beagle-cross (2), and hound-cross (7) bitches ranging from 7.5 to 27.5 kg (16.5 to 60.6 lb) were enrolled in the study. After the onset of spontaneous proestrus, determined on the basis of appearance of serosanguineous vaginal discharge, serum progesterone assays, vaginoscopy, vaginal cytologic evaluation, and vaginal impedometry were performed daily until approximately 4 days after peak LH concentration (day 0) as measured by radioimmunoassay. Vaginal impedometry was compared against serum progesterone concentration measurement, vaginal cytologic evaluation, and vaginoscopy as a method for accurately identifying the LH peak and therefore the optimal breeding time. Ten of 12 bitches were bred with subsequent assessment of embryos.

RESULTS: Vaginal impedometry accurately predicted the preovulatory LH peak in 5 of 11 bitches. One bitch was removed from the study because data were not collected. Of the remaining 11 bitches, 6 had their LH peak on the day serum progesterone concentration first exceeded 2 ng/mL. Crenulation scores reached 1 (mean, 1.3; 95% confidence interval, 0.8 to 1.7) on day 0 as expected; however, these scores were not significantly different from those on days -1 or 1. Vaginal epithelial cell populations did not change noticeably on day 0. Nine of the 10 bitches that were bred produced viable embryos.

CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that daily use of vaginal impedometry in bitches was unreliable as a method for monitoring periovulatory events. All techniques evaluated (ie vaginal impedometry, serum progesterone concentration assays, vaginoscopy and vaginal cytologic evaluation) frequently produced inaccurate results when used individually. Multiple methods should be used to identify optimal breeding time in dogs.