RESUMO
The aim of this study was to evaluate some physiological parameters as total locomotor activity and subcutaneous temperature in two different bovine breeds under tropical environment. In this study, total locomotor activity and subcutaneous temperature were evaluated in 18 clinically healthy female cows. All cows were divided into 3 groups: group A1 was constituted by 6 Holstein Bos taurus, group A2 was constituted by 6 female Herford Bos taurus cows, and group B was constituted by 6 female Bradford Bos indicus cows. Data recording of total locomotor activity (TLA) and subcutaneous temperature (ST) was performed by means of a subcutaneous thermometer (Thermocron) and an actimeter ACTIWATCH® (Cambridge Neurotechnology Ltd.) based on accelerometer technologies equipped on all subjects to record TLA. At the same time, thermal and hygrometric recording were carried out, considering the subtropical climate of Santa Fe. The application of GLM for statistical analysis showed a significant effect (P < 0.05) on statistical model and time of the day on TLA and ST for all groups; no significative effects on animal parameters were found for ST and TLA except for group B. Circadian parameters have been evaluated according to the single cosinor procedure of ST that showed a diurnal daily rhythmicity for all investigated groups and TLA which is focused almost during the photophase for groups A1 and A2 and during scotophase for group B. Considering different species and breeds, and different environmental conditions, this study suggested that some subjects may be much more able to adapt themselves to environmental stress than others. During their evolution from Bos taurus, zebu cattle (Bos indicus) have acquired genes that confer thermotolerance. Subjects from Bos indicus breeds are better able to regulate body temperature in response to heat stress than Bos taurus subjects.