Monitoring Behavior and Welfare of Cattle in Response to Summer Weather in an Arizona Rangeland Pasture Using a Commercial Rumen Bolus.

The effect of weather on the welfare of cattle grazing rangelands has received little study. The objective of this case study was to evaluate the effectiveness of a commercial rumen temperature bolus in monitoring changes in cattle body temperature and behavior during the summer on Arizona rangelands. Ten 2-year-old Corriente heifers were monitored by using SmaXtec Classic Boluses from 1 June to 29 August 2023. The bolus and weather data were averaged and analyzed on 3 and 24 h time scales. The bolus outputs included an activity index, a water intake index, the reticular temperature (RT) and the adjusted reticular temperature (ART, adjusted for drinking events). Weather metrics included the wet bulb globe temperature (WBGT), relative humidity (RH), ambient temperature (AT), wind speed, solar load and temperature-humidity index (THI). Weather variables were independently evaluated as a fixed continuous effect with linear, quadratic and cubic functions. The relative humidity and WBGT were better predictors of bolus metrics than other weather variables. Using 24 h data, the ART initially decreased by 0.4 °C as the WBGT increased from 2 °C to 15 °C, but the ART increased by over 0.15 °C with increasing WBGTs up to 24 °C. As the relative humidity increased, a proprietary bolus activity index initially increased with increasing RH to 45%, remained relatively constant until 65% RH and then increased at more humid levels. A proprietary water intake index decreased with increasing RH. Commercial rumen boluses have the potential to monitor body temperature and identify periods when cattle behavior may be affected by hot weather.