Use of vaginal electrical resistance (VER) to predict estrus and ovarian activity, its relationship with plasma progesterone and its use for insemination in buffaloes

In three experiments we studied the baseline and changes in VER during diff erent natural estrous cycle stages (n=146) in ovarian structures and in pla sma progesterone during estrus induced by prostaglandin injection (n=16) an d the VER at insemination (n=90) in an attempt to predict estrus, ovulation and the best VER range for inseminating buffaloes for optimum conception. The baseline VER was classified on the basis of ovarian findings and estrou s cycle stages. The mean VER during estrus, metestrus, diestrus, proestrus and anestrus was 32.68 +/- 0.46, 41.26 +/- 1.17, 50.23 +/- 0.55, 43.20 +/- 0.64 and 55.86 +/-0.57 ohms, respectively. There was a significant differen ce (P <0.01) between the VER except those between metestrus and proestrus. The ANOVA for VER over estrous cycle stages showed a highly significant (P <0.01) effect of stage of estrous cycle on VER in buffaloes. The percent de crease in VER was more pronounced from diestrus to estrus. In the second pa rt of the study plasma progesterone profiles and the appearance of estrus i n buffaloes induced to estrus using two dose schedules and routes of PGF(2 alpha) administration showed that luteolysis and estrus induction was slowe r in the 10 mg IVSM route (Intra Vulvo Submucosal) (only 60% animals evince d estrus in 48 to 72 hours) as compared to the 25 mg IM route (83.33% evide nced estrus in 48 to 72 hrs). Fall in plasma progesterone was synchronous t o a fall in VER, the correlation (0.65) between them being positive and sig nificant (P<0.01). After ovulation the VER started rising, showing a distin ct relationship between VER and ovulation. By using VER, an additional 35.6 % of the buffaloes could be detected in estrus. In the third part of the st udy, insemination of buffaloes induced to estrus (n=11) and normal-estrus b uffaloes (n=79) showed that the overall conception rates to single insemina tion when the buffaloes were inseminated at the VER range of 26 to 30, 31 t o 35 and 36 to 40 ohms were 81.48, 58.97 and 16.66%, respectively. Buffaloe s showing VER from 31 to 35 ohms and 36 to 40 ohms also evidenced atypical and Null fern pattern in the cervicovaginal mucus. The study proved that VE R can be used successfully to predict the stage of estrous cycle, ovarian s tatus and ovulation; and insemination at a tow VER distinctly improves the conception rates in buffaloes. <(c)> 2001 by Elsevier Science Inc.