The intravaginal electrical impedance measurements in monitoring estrous cyclicity, the length of the breeding season and ovarian cysts in goats

Abstract

The aim of this work was to assess the usefulness of the intravaginal impedance measurements in monitoring estrous cycles, indicating ovarian disorders and determining the duration of the reproductive season in goats. Intravaginal electrical impedance at the vagino-cervical junction was measured using the 2-electrode impedometer (shaft diameter 0.6cm; electrode outer diameter 0.8cm, shaft length 21cm). The outer electrode has a diameter of 0.8cm. The first experiment was carried out on 8 goats during the mid-breeding season and included 2 consecutive estrous cycles. Intravaginal electrical impedance was measured daily and blood samples were taken at time for plasma concentrations of progesterone (P4) and at 4-h intervals during estrus for detection of the luteinizing hormone (LH) peak. The second experiment was conducted in goats (n=4) in which irregular estrous cycles and presence of follicular cysts had been previously observed. Experiment 3 was performed during the transitional period between the breeding season and anestrus (n=8). During the breeding season, the changes in concentration of P4 were highly correlated with the values of intravaginal electrical impedance (r=0.84; P<0.01), and the profile changes of the intravaginal impedance followed a pattern similar to the changes in P4 concentrations. Reduction in vaginal impedance was closely associated with the onset of behavioral estrus and the LH peak. In peri-estrous period, the intravaginal impedance values were 35.65±0.49Ω and were significantly different (P<0.01) than in the luteal phase (57.39±0.37Ω). Positive correlations and similar profile of changes in the intravaginal impedance and concentrations of P4 were also recorded in goats, in which disorders in the course of the estrus cycle were found, caused by the presence of the ovarian follicular cysts. In these goats both the intravaginal impedance and concentration of progesterone remained constant and low level (32.17±0.53Ω, and 0.43±0.03ng/ml, respectively). During the onset of the seasonal anestrus, in spite of the remaining low concentration of P4, intravaginal impedance did not show higher fluctuations, and the correlation between these parameters was negative (r=−0.31; P<0.01). In conclusion, the results demonstrated that measurements of the intravaginal impedance can be useful to monitor the estrous cycle and in goats. Our preliminary results also suggested the usefulness of measurements of intravaginal impedance in signaling the presence of ovary cysts in goats. However, these studies require further follow-up. Moreover, measurements of the intravaginal impedance can constitute an information about the onset of the seasonal anestrus in this animal species.