Dynamics of Vaginal pH in the Bitch during Proestrus and Estrus

Abstract

The aim of this study was to investigate the dynamics of the pH of vaginal secretions during proestrus and estrus in bitches and its association with the optimal time for insemination and the values of steroid hormones. Sixteen bitches from different breeds and age were included in this investigation. Vaginal pH of each bitch was measured once daily, starting from the first day of vulval bleeding and continuing until the first day of cytological diestrus. In each bitch vaginal smears were taken to determine the onset of estrus and diestrus and blood samples were taken to determine serum progesterone (ng/ml) and estradiol-17β (pg/ml) for detection of the onset of ovulation and their influence on values and the dynamics of vaginal pH. Vaginal pH values in the bitches at the first day of proestrus were between 7.4 and 8.7. This parameter decreased with the progress of the proestrus and the entering into the estrus. Compared to the rest of the estrus, at the time of ovulation and on the next day, a consistent decrease of mean values (6.61±0.15 and 6.63±0.15 respectively) was observed (р<0,01). Individually at the time of ovulation vaginal pH ranged between 6.5 and 6.8. In the days following ovulation a gradual increase in mean values was detected. At the first day of diestrus vaginal pH values were measured significantly higher than those in estrus (р<0,001) and were between 7.4 and 8.3 (7.74±0.26). In our study we found that the vaginal pH values in the bitch are lowest at the time of ovulation, with individual variations and exceptions.