Comparison of Tympanic and Tail Temperatures in Angus and Brahman Steers

Abstract

In cattle, core body temperature can be used as an important indicator of heat stress level. However, accurately recording core body temperature can be difficult and labor intensive. The objectives of the current study were 1) to compare the recorded tympanic and tail body temperature measurements in steers and 2) to determine the body temperature change of Angus and Brahman steers in a hot and humid environment. Data was analyzed using a repeated measure model where repeated measures were hourly tympanic and tail temperatures and their difference for individual steers during the day of the experiment. There was a significant breed effect (P=0.01), hour (P<0.0001) and breed by hour interaction (P<0.0001) for the tympanic temperature. Brahman steers, which are known to have superior thermotolerance, maintained a lower body temperature than the Angus steers during the afternoon under grazing conditions. In the Brahman steers there was only a minimal increase in the body temperature throughout the day, an evidence of the thermotolerance ability of the breed. In the Angus steers, which experienced an increase in their body temperature from hour to hour with a peak around 1600 hour; there was a significant difference between the tympanic and tail temperature during the times when the body temperature as measured by the tympanic recordings was the highest (1300 to 1700 hour). Our results indicate that the tympanic temperature can be used to accurately and continuously monitor core body temperature in a natural environment for up to several days and without disturbing the animal.