Canine ovulation timing: A survey on methodology and an assessment on reliability of vaginal cytology.

Ovulation timing in bitches is a routine procedure in small animal practice around the world. It is most frequently used for supporting breeding management, high-risk pregnancy monitoring and determination of the time of parturition. To learn more about how and for what reasons veterinarians interested in small animal reproduction perform canine ovulation timing, an online survey was conducted in 2017. The link to the survey was distributed via the mailing list cafereprod-l@list.cornell.edu and the website, the Twitter account and the Facebook page of EVSSAR. All respondents recommended using quantitative progesterone measurement for ovulation timing alone or in combination with other diagnostic tests. Vaginal cytology was also a commonly used technique. The 63 respondents followed different protocols for sampling and staining vaginal epithelial cells. Interestingly, 50 respondents used vaginal cytology routinely, but only two consider it as a very reliable and another nine as a somewhat reliable test if used alone. In a second project, delegates attending the EVSSAR congress held in Vienna, Austria, in June 2017 had the opportunity to examine seven stained vaginal smear slides under optical microscopy in a blinded approach. The results showed a marked heterogeneity in the identification of vaginal cells and assessment of the time in relation to ovulation. This heterogeneity supports the opinion of survey participants that vaginal cytology alone is not a valid tool for determining the day of ovulation. Results of both projects suggest that there is no standard procedure for the examination of vaginal smears in dogs. It is not recommended to determine the optimal time for mating based on the examination of a single vaginal smear only. According to some comments of survey participants, it is more useful to assess vaginal samples repeatedly and to use the findings to determine when to start progesterone measurement.