Technical note: The use of a telemetric system to continuously monitor ruminal temperature and to predict ruminal pH in cattle

The objective of this study was to compare a telemetric monitoring system to an existing in situ methodology (conventional system) of monitoring ruminal temperature and to validate its use to detect changes in ruminal pH (RpH). Four nonlactating, ruminally cannulated Holstein dairy cows (760±30kg of body weight, mean±standard deviation) housed in a tie-stall facility were used in the study. The experiment was conducted during the month of May and the recorded ambient temperature was 8.0±2.0°C (mean±SD). The cows were fed a diet consisting of chopped mixed hay (MH; 11.3% crude protein, 59.7% neutral detergent fiber, 17.3% nonfiber carbohydrate, 3.1% ether extract, and 11.3% ash; dry matter basis) during wk 1 and were gradually switched to a high-grain (HG) diet (11.6% crude protein, 30.2% neutral detergent fiber, 50.7% nonfiber carbohydrate, 3.0% ether extract, and 6.0% ash; dry matter basis) during wk 2. A conventional system that utilized an indwelling electrode was used to monitor RpH and ruminal temperature (RTC) during d 6 and 7 of each week. The indwelling electrode was attached to a telemetric bolus and ruminal temperature (RTT) was logged into a personal computer. The daily mean, minimum, and maximum RpH and duration (min/d) RpH 38.6°C. These increases were not detectable with the telemetric system. Ruminal temperature obtained by the conventional system was 0.68°C±0.005 lower than RTT during MH feeding (wk 1), whereas RTC was 0.04°C±0.004 higher than RTT during HG feeding (wk 2). Daily minimum RpH was associated with maximum daily RTC and RTT during MH and HG feeding (R2=0.88 and 0.43, respectively). There was a high association between low RpH and high ruminal temperature, with the highest associations being between duration (min/d) of RpH 39.0°C (R2=0.68) and RTT >39.2°C (R2=0.72). Unlike the telemetric system, the conventional sys