Estrous detection by monitoring ventral tail base surface temperature using a wearable wireless sensor in cattle

In the present study, the ventral tail base surface temperature (ST) was monitored using a wearable wireless sensor for estrus detection in cattle. Relationships among ST, behavioral estrus expression, ovulation, and changes in hormone profiles during the estrous cycle were examined. Holstein Friesian or Japanese Black female cattle were used in summer (August-September), autumn (October-November) and winter (January-February; three animals per season). On Day 11 of the estrous cycle (Day 0 = the day of ovulation), the sensor was attached to the surface of the ventral tail base and ST was measured every 2 min until Day 11 of the next estrous cycle. Hourly maximum ST values were used for analysis. To exclude circadian rhythm and seasonal effects, ST changes were expressed as residual temperatures (RT = actual ST − mean ST for the same hour on the previous 3 days). Obvious circadian rhythms of the ST were observed and daily changes in the ST significantly differed among seasons. There was no significant seasonal difference, however, in the RT. The mean RT increased significantly ∼24 compared with ∼48 h before ovulation. The mean maximum RT was 1.27 ± 0.30 °C, which was observed 5.6 ± 2.4 h after the onset of estrus, 2.4 ± 1.3 h before LH peak, and 26.9 ± 1.2 h before ovulation. The ST of the ventral tail base could be monitored throughout the estrous cycle and could detect a substantial change around the time of expression of behavioral estrus. Calculation and analysis of the RT could be useful for automatic estrous detection.