Variabilidade espacial do microclima em sistema compost barn: influência na qualidade da cama, termorregulação e comportamento de vacas leiteiras

Abstract

The objective of this research was to verify if the spatial variability of the microclimate in the compost barn system has influence on the thermoregulation and behavior of dairy cows and on bed quality. The experiment was carried out between October 2017 and February 2018, with evaluations performed preferably at weekends, in private property located in the interior of the municipality of Dois Vizinhos - Paraná. We used 18 cows of the Dutch breed x Jersey which were divided into two treatments according to the order of lactation. The first treatment consisted of primiparous cows and the second was multiparous cows. Evaluations were made regarding thermoregulation through respiratory rate and surface temperature; microclimatic assessments (air temperature, relative air humidity and wind speed) and; temperature and humidity of the bed, to evaluate the spatial variability of these variables, microclimatic evaluations for thermal comfort indices and behavioral evaluations. The data regarding spatial variability were analyzed through geostatistics and the data referring to the indices of thermal comfort, thermoregulation and behavior were analyzed through Bayesian inference. The thermal environment of the microclimate of compost barn presented spatial dependence for all analyzed variables. Thermal comfort indexes indicated that compost barn provided conditions for the animals to remain in thermal comfort, which was confirmed by the respiratory rate and surface temperature of the animals' fur. Although comfort indexes and physiological responses indicated thermal comfort, cow behaviors were shaped by the thermal environment and social structure, with differences between treatments for eating behavior, water intake, gait and rest leisure. The results found in this research indicate that compost barn is a system capable of providing thermal comfort conditions for dairy cows. However, a well-sized ventilation system is required throughout the installation area so that the movement of the air mass refreshes the animals and helps to remove the moisture from the bed.