Evaluation of a new approach for the estimation of the time of the LH surge in dairy cows using vaginal temperature and electrodeless conductivity measurements

The objective of the study was to test the effectiveness of a new type of conductivity sensor, along with vaginal temperature, at identifying the LH peak associated with estrus in dairy cows. Twelve mature non-lactating Holstein–Friesian cows had their estrous cycles synchronized on two occasions, and then data were collected for the following spontaneous cycles. An indwelling electrodeless plastic-coated toroidal conductivity sensor, which also recorded temperature, was placed in the vagina throughout the cycle. Blood samples were collected for LH measurement, and ultrasound scanning used to confirm ovulation. Although there was a relationship between vaginal mucus conductivity measured by the toroidal sensor and the timing of the LH surge, it was not sufficiently robust in individual cows to be able to identify the time of the LH surge. The mean increase in vaginal temperature at estrus was 0.48 °C. An algorithm was developed which used the detected individual cow temperature peak to test the relationship with the LH peak. In 16 out of 21 cases where ovulation was confirmed and data existed, the estimated individual peak was within 4 h of the LH surge, in three cases it was ±6 h, and in two instances it was early. In conclusion, the temperature algorithm was able to identify the time of the LH surge and thus predict time of ovulation in a way that would allow effective AI, although this result needs to be tested in lactating cows. However, the toroidal conductivity sensing method was not able to produce data of sufficient quality to develop a predictive relationship in individual cows.