Spatial analysis of microclimatic variables in compost-bedded pack barn with evaporative tunnel cooling

Abstract

In this study, we aimed to assess the spatial variability of microclimate inside a closed compost-bedded pack barn (CBP) with a negative ventilation system during summer and winter. The research was carried out in a CBP located in the Zona da Mata region, Minas Gerais, Brazil. For each of the stations analyzed, the following environmental mean variables observed inside a CBP were measured: air dry-bulb temperature (t db ), air relative humidity (RH), and windspeed, Temperature-Humidity index, and specific enthalpy. The kriging maps showed that the most critical housing conditions in the thermal environment were found, mainly, from the central part of the CBP, close to the exhaust fans. The analyses also pointed out that the system presented temperature gradients along the length, up to 3°C. During the summer afternoon, the entire region of the CBP was in a discomfort situation (t db >26°C; RH>75%). During the winter, the measured environmental data remained within the comfort zone throughout the facility. However, probably due to the lack of thermal insulation of the material used to close the sides of the CBP, it did not allow spatial thermal uniformity for both seasons.It was also inefficient to keep the animals within the comfort zone for lactating cattle during the critical summer period.

Mapping of the Thermal Microenvironment for Dairy Cows in an Open Compost-Bedded Pack Barn System with Positive-Pressure Ventilation

“…The low CV values obtained are also an indication that the variables had approximately uniform distribution. These results corroborate those described by Andrade et al [ 27 ], who evaluated a closed CBP system in the same region where this study was conducted, and obtained CV values below 0.12.…”

“…The THI results achieved in this study ( Figure 6 a,c,e,g) corroborate those observed by Andrade et al [ 27 ], who evaluated the microclimatic variables in a closed CBP system with a tunnel-mode ventilation associated with AECSs, in the same climatic region as this study. In the latter study, it was observed that the highest mean THI levels occurred in the afternoon period, but were always lower than 74.0, being within the thermal comfort range for lactating dairy cows.…”

“…Certainly, t db exerts a strong influence on the thermal comfort and productive performance of dairy cattle, but this variable should always be evaluated in association with RH [ 15 , 29 ]. Through Figure 5 b,d,f,h, it can be observed that the RH spatial distribution maps denoted greater spatial variability, in accordance with what was observed in other studies conducted in CBP systems [ 21 , 27 ], with the occurrence of high RH amplitudes. In the dawn, morning, afternoon, and night periods, ranges of 6.2, 10.1, 12.4, and 10.4% were observed, respectively, indicating the heterogeneous distribution of RH inside the facility.…”

“…Since the evaluated system did not use adiabatic evaporative cooling systems (AECSs), high RH levels may represent a problem for the semi-composting process and bed management, as well as animal health and milk quality [ 2 , 8 ]. In fact, in this type of system there is a tendency to obtain elevated RH levels in the internal environment, because of steam released during the semi-composting process, evaporation and water spillage from tipper drinkers, and the animals’ respiration and waste [ 10 , 27 ]. For this reason, it is necessary to pay greater attention to bed management, with more revolving operations, along with the addition and incorporation of more dry bedding material, to reduce bed moisture and keep the resting area dry, hygienic, and comfortable for the animals [ 8 ].…”

“…The average daily t db and RH data obtained in four periods of the day were used: dawn (12:00 a.m. to 05:59 a.m.), morning (06:00 a.m. to 11:59 a.m.), afternoon (12:00 p.m. to 05:59 p.m.), and night (06:00 p.m. to 11:59 p.m.). This division was carried out with the objective of identifying the occurrence of critical environmental conditions, according to the methodology adapted by Andrade et al [ 27 ].…”