Evaluation of physiological responses of calves during rainy season in the semiarid environment

Abstract

The aim of this study was to evaluate the physiological responses of calves during rainy season. The respiratory rate (RR), rectal temperature (RT), and surface temperature (TS) of 23 calves were measured during the period from 7:00 to 18:00 h. Air temperature (A), relative humidity (RH), wind speed (U) and mean radiant temperature (MRT) were also measured. With a portable thermographic camera, thermal images were obtained and four body regions were chosen (face, neck, body and legs). The analysis of variance (ANOVA) revealed a significant effect of day period on the RT and TS, but not for the RR. The ANOVA also found a significant effect of body region on the TS, where the thermographic analysis revealed that the facial region showed higher temperature than other body regions. Thus, it is concluded that the calves maintained their body temperature at normal levels throughout all day without the need for activation of heat loss by respiratory evaporation, which shows a situation of thermal comfort. There are regional differences in the TS, where the body regions that have higher temperatures are responsible for most of the high sensible heat loss, as the face.