RESUMEN
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.
RESUMEN
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.
This study aimed to evaluate the influence of cooling systems, ventilation and nebulization on the physiology and behavior of Holstein cows housed in free-stall during the summer of southeastern Brazil. 20 Holstein cows were subjected to two treatments with and without cooling system. Environmental parameters dry bulb temperature, relative humidity and black globe temperature were also recorded. Rectal temperature and respiratory rate were evaluated at 5h, 9h30min, 11h30min, 13h30min, 16h30min, 18h30min e 21h30min. The behavioral variables recorded were posture and activities from 5h to 21:30h. Statistics we done using the method of least squares means. Despite the statistical differences obtained for the physiological variables, they were not biologically effective and indicated that the animals were in thermal comfort. Animals that had ventilation and nebulization have eaten even during the hottest hours of the day. The cooling system is a strategy that allows greater thermal comfort to animals and therefore can optimize milk production by increasing the dietary intake.