[Measurement of stress parameters in farm animals using active telemetry]

We investigated the effect of an acute stressor on body temperature and heart rate in cows. Both parameters were recorded by active telemetry. For the experiments, five cyclic Brown Swiss cows were used, each of them exposed to an acute stressor during estrus and the luteal phase of the cycle. The stressor consisted in restraining the cows in a crush for hoof treatments. During the 2-hour stress period and for additional 6 hours, body temperature and heart rate were measured every 10 minutes. Control animals remained in their accustomed environment during the whole experiment of 8 hours. The course of body temperature and heart rate was clearly influenced by the stressor. While heart rate was maximal already at the beginning of the stress period, the body temperature showed highest values only one hour after stress and then continuously decreased. Changes in body temperature and heart rate under stress differed significantly from the values of control animals. Both parameters are reliable indicators of stress in the bovine species. The transmitters used in this investigation allowed us to register exact data without manipulation of the animal, which could possibly falsify the results. This advantage as well as the functional longevity of the transmitters (ca. 6 months) make active telemetry a useful tool for stress research in farm animals.