Abstract:

[Objective] This study was conducted to measure and compare the electrical resistance of vaginal mucus （ERVM） of beef cows in different reproductive physiological periods and with different types of reproductive disorders, and to provide references for the assistant detection of estrus and gestation as well as the diagnosis of reproductive disorders in cows based on the obtained relevant basal data. Meanwhile, it also aimed to assess the applicability of animal estrus and ovulation tester, and to render technical support for improving the reproductive efficiency in cows. [Method] A total of 297 reproductive beef cows were selected from 21 cattle farms or households. According to the reproductive records and rectal examination results, the cows were subjected to reproductive physiological periods （anestrous period, estrus period, gestation period) determination or reproductive disorders diagnosis. Based on the above records and results, the 297 cows were assigned into the following four groups: an anestrous period group （n=76）, an estrus period group （n=48）, a gestation period group （n=106）, and a reproductive disorders group （n=67）. The 106 heads in the gestation period group were further classified based on the gestation days: 44 heads with ≤60 days of gestation, 24 heads with 61-120 days of gestation, 31 heads with 121-180 days of gestation, and 7 heads with >180 days of gestation. In accordance with the reproductive physiological processes, 42 heads at the luteal phase, 13 heads at the follicular phase and 24 heads at the gestation phase were selected from the cows in the anestrous, estrus, and gestation periods, respectively. The 67 heads in the reproductive disorders group were further divided based on the types of reproductive disorders: 8 heads with ovarian cysts, 57 heads with persistent corpus luteum, and 2 heads with freemartinism. The ERVM of the cows in different reproductive physiological periods and with different types of reproductive disorders was measured using a fully automated animal estrus and ovulation tester, and was statistically compared and analyzed. [Result] The lowest ERVM was observed in the cows in the estrus period, which was 17.91% （P<0.01） and 28.38% （P<0.01） lower than that in those in the anestrous and gestation periods, respectively; the ERVM in the anestrous period was 12.76% （P<0.01） lower than that in the gestation period. The highest ERVM was observed in the cows with ≤ 60 days of gestation, followed by those with 61-120 days of gestation; both were extremely significantly （P<0.01） higher than those with >180 days of gestation; the ERVM in the cows with 121-180 days of gestation was significantly （P<0.05） higher than that in those with >180 days of gestation. The ERVM in the cows at the follicular phase decreased by 35.85% and 37.05% compared with that in those at the luteal and gestation phases, respectively, reaching extremely significant （P<0.01） levels; the ERVM at the luteal phase was similar to that at the gestation phase （P>0.05）. The ERVM in the cows with freemartinism was the highest, and was 36.12% higher （P<0.01） than that in those with ovarian cysts; the ERVM of the cows with persistent corpus luteum was 22.42% higher than that in those with ovarian cysts （P>0.05）. [Conclusion] The variations in the ERVM of beef cows in different reproductive physiological periods and with different types of reproductive disorders were characterized. The average ERVM of the cow populations evidently varied among the anestrous, estrous and gestation periods as well as the different types of reproductive disorders, and also exhibited apparent individual differences. Moreover, there was partial overlap in the ERVM of cows under different reproductive physiological conditions. A ERVM less than 180 Ω was indicative for the determination of estrous period. Additional diagnostic techniques, such as rectal examination and verification of reproductive records, were necessary when using ERVM to identify gestation and anestrous periods and to diagnose reproductive disorders in cows.

Key words: cow, reproductive physiological period, gestation, reproductive disorder, electrical resistance of vaginal mucus