USE OF A VAGINAL MUCUS IMPEDANCE METER TO DETECT ESTRUS IN THE COW

Two experiments were conducted to investigate the efficacy of a vagina l mucus impedance meter for the detection of estrus in the dairy cow. In Experiment 1 the positioning of the probe within the vaginal tract was examined in dairy cows (n=6) by measuring mucus impedance at 5-cm intervals during probe withdrawal and comparing these fixed distance m easurements with the depth within the vaginal tract at which the lowes t impedance measurement was recorded. Measurements at 15 and 20 cm fro m the vulva were significantly lower than at other fixed depths, but d id not show a reduction during estrus. The lowest recording upon withd rawal of the probe, which usually occurred between 15 and 20 cm from t he vulva, was significantly lower than at any fixed depth recordings a nd was reduced proportionate during estrus to 0.14 of its non-estrus v alue. In Experiment 2 the accuracy of the probe to confirm estrus in c ows exhibiting possible estrus signs was examined. Dairy cows (n=191) were inseminated either on the basis of herdsman observation of behavi or alone (Treatment A) or on the basis of herdsman observation with co ws exhibiting signs of estrous behaviour, but not standing to be mount ed, being tested for vaginal mucus impedance (Treatment B). There were no significant treatment differences in the estrus detection rate, co nception rate or other reproductive performance parameters. However, i n 12% of cows in Treatment B, measurement of vaginal mucus impedance d etected an extra estrous event, giving a theoretical increase in the e strus detection rate from 0.67 to 0.74 detected/predicted estrous even ts. It was concluded that when using a vaginal probe the lowest value in the vaginal tract should be sought, but that using the probe as an adjunct to herdsman's observation would not greatly increase estrus de tection rate.