This study employed infrared thermography to assess the thermoregulatory responses of female buffaloes reared in a hot and humid climate as a function of variations in time and the thermal environment, and to correlate rectal temperature with that of different body areas. The trial was carried out at Embrapa Eastern Amazon (01 • 26'S and 48 • 24'W) in Belém, PA, Brazil. Twenty-four female buffaloes fed exclusively on pasture and exposed to the sun throughout the day in an open area were used. The animals were taken back to the corral at 6 A.M., 9 A.M., 12 P.M., 3 P.M., 6 P.M., and 9 P.M. for measurements of rectal temperature (RT), respiratory rate (RR), and body surface temperature (BST) using infrared thermography (IRT). Data on air temperature (AT), relative air humidity (RH), wind velocity (WV), and solar radiation (SR) were also recorded. A quadratic effect of AT, RH, SR, RR, and RT (P < 0.01) was found as a function of measurement time. Between 12 P.M. and 3 P.M., AT, SR, RR, and RT values were the highest, while RH values were the lowest (P < 0.05). WV was the highest between 12 P.M. and 9 P.M. A difference was found in RR and RT among the day's times, with the highest values at 12 P.M. and 3 P.M. (P<0.05). The IRTs have a quadratic effect as a function of day's times, with the highest levels between 12 P.M. and 6 P.M. and a reduction at 9 P.M. All IRTs are correlated with the physiological variables RR and RT, except for the IRT of the side of the back, which is not correlated with RT. The IRTs of the eye and cheek are correlated with RT (P < 0.01) and with RR (P < 0.05). IRT was efficient in evaluating the thermal stress of female buffaloes in hot and humid climates, and the technique can be used to evaluate the body temperature of these animals, since the RT was positively correlated with the temperature of the eye and cheek.

Este estudo teve como objetivo avaliar a influência de recursos de climatização, ventilação e nebulização, sobre a fisiologia e o comportamento de vacas Holandesas alojadas em free-stall, durante o verão do sudeste brasileiro. Foram utilizadas 20 vacas Holandesas submetidas a dois tratamentos com e sem climatização. Os parâmetros ambientais registrados foram temperatura de bulbo seco, umidade relativa do ar e temperatura de globo negro. As variáveis fisiológicas avaliadas foram temperatura retal e frequência respiratória. As variáveis comportamentais registradas foram postura e suas atividades dentro da instalação. Para análise estatística utilizou-se a metodologia de quadrados mínimos por meio do procedimento PROC MIXED e PROC GLM. Apesar das diferenças estatísticas obtidas para as variáveis fisiológicas, as mesmas não foram biologicamente efetivas e indicaram que os animais se encontravam em conforto térmico. Os animais que dispunham de ventilação e nebulização alimentaram-se mesmo nas horas mais quentes do dia. A climatização é uma estratégia que permite maior conforto térmico aos animais e por consequência pode aperfeiçoar a produção leiteira através do aumento no consumo alimentar.

Climate change is seen as a significant threat to the sustainability of livestock production systems in many parts of the world, particularly in tropical regions. Extreme meteorological events can result in catastrophic production and death of livestock. Heat waves in particular can push vulnerable animals beyond their survival threshold limits. However, there is little information about buffalo responses to sudden changes in the thermal environment, specifically the heat waves. This study aimed to quantify the thermoregulatory and blood biochemical responses of heat-acclimatized buffaloes to a simulated heat wave. The experiment was designed in a climatic chamber with two periods of 4 days each. Twelve heat acclimated buffalo heifers aged 18 months were used. The climatic chamber environment was set as follows: 4-day period (P1) simulating the same weather conditions of a summer in humid tropical climate used as a baseline, with daily cycle with Ta and RH at 27 ± 1 °C and 76% from 0600 h to 1900 h and 24 ± 1 °C and 80% from 1900 h to 0600 h, and 4-day period (P2), simulating a daily heat wave cycle, from 0600 h to 1900 h with Ta and RH kept at 36 °C and 78% and from 1900 h to 0600 h, 27 °C and 74%. All animals were subject to both treatments and data were analyzed by a repeated measure analysis of variance, with post-hoc pooling comparison performed by Tukey’s test. In P2, there was observed a significant increase in respiratory frequency (p < 0.01), found four times in P1. The sweating rates were quite high in both periods; still, there were significant increases in P2 compared to P1 (p < 0.01) (4931 and 3201 g/m2/h, respectively). A slight but significant increase in rectal temperature was observed during the day (p < 0.01), with a rising until 1900 h. The simulated heat wave in P2 did not affect the values of the erythrogram or leukogram, excluding the significant reduction in K+ (p < 0.05). The low heat storage and the subsequent fast and full recovery of the thermal balance late afternoon appear to be related to the high sweating rate values. The massive sweating rate emphasizes its relevance in the maintenance of buffalo homeothermy. The absence of changes in hematological parameters has revealed the considerable physiological resilience of buffaloes toward simulated heat waves.