Avaliação da adaptabilidade de vacas leiteiras criadas no Cariri Cearense durante a época quente e úmida

Abstract

In tropical climates such as that of Northeastern Brazil, climatic elements such as air temperature and humidity exert a pronounced effect on living organisms, often limiting animal development, production, and reproduction due to the associated stress. Therefore, studies that monitor animal adaptability under diverse climatic conditions are of great importance. Thus, the objective of this study was to evaluate the adaptability of dairy cows raised in the Cariri region of Ceará during the rainy season, which is characterized as hot and humid. The study was conducted on two farms (5 km apart) located in the municipality of Crato. Data collection took place during the rainy season, from November to April, comprising three periods (Times): T1—December/January (beginning of the rainy season); T2—February/March (mid–rainy season); and T3—April (end of the rainy season). Records of ambient temperature (AT) and relative humidity (RH) were obtained both under direct sunlight and in the shade. Based on these climatic variables, the Temperature and Humidity Index (THI) was calculated for sun exposure (THI_sun) and shade (THI_shade). Animal thermography and rectal temperature (RT) measurements were performed during the afternoon milking period (13:30–15:30), along with the recording of climatic variables. Reactivity was assessed at the time of rectal temperature measurement. The data were subjected to statistical analysis, showing that THI_sun was consistently higher than THI_shade, as expected, with values exceeding 81, indicating that the animals were exposed to critical conditions. Overall, surface temperatures were high, ranging from 36.19 °C (forehead surface temperature, Girolando, Time 2) to 39.52 °C (udder surface temperature, Jersolando, Time 2). The rectal temperature of the Girolando genotype was 38.87 °C at the beginning of the rainy season (T1), representing the lowest overall value, while the highest RT was observed in the Jersolando genotype (39.52 °C) during the mid–rainy season (T2). The Girolando group showed an average reactivity score of 1.03, whereas the Jersolando group presented a significantly higher mean value of 1.72. This suggests that, on average, individuals in the Jersolando group exhibited greater reactivity compared to those in the Girolando group. The results of this study highlight the importance of considering both genetic factors and local climatic conditions in dairy cattle production. Thus, cows with a predominance of the zebu genotype (Girolando) exhibited lower surface and rectal temperatures, reinforcing their greater adaptability to the hot and humid climate of the Cariri region of Ceará.