Evaluation of Heat Tolerance of Tabapua Bovines in the Central Region of Brazil

The aim of this research was to evaluate the heat tolerance of Tabapuã bovines exposed to the heat tolerance test in the central region of Brazil. Eleven male bovines of the Tabapuã breed were used, with average age and average weight of 24 months and 539.33 ± 59.86 kg, respectively. The experimental design was completely randomized. In the evaluation of heat tolerance, a thermolytic capacity test . The thermolytic capacity test was replicated on five non-consecutive hot, sunny, cloudless days. This test consisted of the measurement of rectal temperature (RT) of the animals at three different times, obtaining the thermolytic capacity index (TCI). For the calculation of TCI the following formula was used: TCI = 10-[(RT2-RT1)-(RT3-RT1)]. The RT1 was measured at 1:00 p.m., immediately after the animals had remained for two hours in the shaded corral (11:00 a.m. to 1:00 p.m.). The RT2 was obtained at 2:00 p.m., immediately after the animals had stayed an hour in a corral with incidence of solar radiation (1:00 p.m. to 2:00 p.m.). The RT3 was measured at 3:00 p.m., immediately after the animals had stayed an hour in a shaded corral (2:00 p.m. to 3:00 p.m.). The RT was measured with the aid of a digital clinical thermometer, introduced and kept in the rectum of the animal for one minute. The mean RTacross the three schedules evaluated was 38.76 ^oC, indicating good adaptability of Tabapuã breed to the tropical environment. Considering the evaluating of RT, there was a significant difference (P<0.05) between the averages recorded with the animals in the shade (38.35 ^oC) and after one hour of sun exposure (39.47 ^oC), with an increase of 1.12 ^oC. At the end of the test, after one hour of exposure to shade, RT decreased (P>0.05) numerically by 1.0 ^oC to 38.47 ^oC, . The result of the average TCI was 9.07, with minimum and maximum values of 8.80 and 9.41, respectively, considering the average of all the animals in the five days of evaluation. The results obtained in this study showed that the Tabapuã breed has a good heat tolerance.