Influência da ambiência nos indicadores termofisiológicos de bovinos em feira agropecuária no Nordeste

Abstract

The state of Ceará is characterized by a semi-arid tropical climate, with high temperatures and intense solar radiation, which makes it challenging for cattle to maintain homeothermy. This study aimed to evaluate the physiological parameters of cattle during the 65th EXPOECE in Ceará. A total of 35 adult cattle from the Pardo-Suíço, Jersey, Girolando, Gir, Guzerá, Sindi, and Nelore breeds were housed in a collective shelter. Temperature and relative humidity data were collected using a data logger to calculate the temperature-humidity index (THI). Respiratory frequency was measured by observing flank movements for 15 seconds and multiplying by 4. Surface temperature was assessed using infrared thermography and analyzed with the IR Reporter® software. Measurements were taken at 07:00, 12:00, and 18:00. The results showed that the air temperature was highest at noon (33.0 °C; p<0.05), with a THI of 82.6. At this time, cows from the Jersey and Girolando breeds exhibited the highest respiratory frequencies (86.9 and 63.5 movements per minute, respectively; p<0.05). The Pardo-Suíço and Sindi breeds showed similar respiratory frequencies between 07:00 and 12:00 but were higher compared to 18:00 (63.5 vs 50.9 mov/min and 62.7 vs 46.9 mov/min, respectively; p<0.05). Cattle from the Guzerá breed had higher respiratory frequencies at noon compared to 07:00 (30.1 vs 22.1 mov/min; p<0.05). The Nelore breed had the lowest respiratory frequency in the morning (25.3 mov/min; p<0.05), while the Gir cows did not show significant differences between the time points. Regarding surface temperature, cattle from the Pardo-Suíço, Girolando, Gir, Guzerá, Nelore, and Sindi breeds had higher temperatures at noon (36.8; 36.7; 36.0; 36.2; 36.8; 36.4 °C, respectively; p<0.05). Jersey cows had the highest surface temperature at noon only when compared to the late afternoon (36.5 vs 35.4 °C; p<0.05). The forehead temperature was highest at noon for all breeds except Jersey, which had a lower temperature in that region at 18:00 (34.3 °C; p<0.05). The trunk temperature was higher at noon for all breeds except Jersey, which did not show significant differences. The temperature of the rump was higher at noon for the Jersey, Pardo-Suíço, Girolando, Guzerá, and Nelore breeds, while for the Gir and Sindi breeds, it was higher only compared to 18:00. The ocular temperature was also higher at noon for most breeds, except for Jersey, which did not show significant differences. In conclusion, under conditions of greater thermal discomfort, especially at noon, the cattle, especially those in lactation, exhibited increased surface temperature and respiratory frequency during the agricultural exposition in northeastern Brazil.