## 2 Materials and Methods
### Signal Monitoring  
The experiment was carried out in the city of Pirassununuga, state of Sao Paulo, Brazil (latitude 21\({}^{\circ}\)59\({}^{\prime}\)46\({}^{\prime\prime}\) south and longitude 47\({}^{\circ}\)25\({}^{\prime}\)33\({}^{\prime\prime}\) west, altitude of 627 m). The signals were acquired from Holstein heifers.  
To develop a method to monitor bovine brain electrical activity, it was necessary to define the sample frequency (Fs), determine where to place the electrodes (positioning and fixation) and equipment, and deal with artifacts and other acquisition issues. These conditions were established by conducting measurements with two animals.  
Considering the frequency range of bovine brain signals reported in the literature [31; 37] and the real-time transmission limitations of the equipment, the Fs was initially set to 100 Hz. This value ensured that frequencies up to 50 Hz were mapped without aliasing. This 50 Hz limit expanded the frequency spectrum observed by the mentioned authors and allowed for the presence of frequency components above 40 Hz, associated with pain and stress [58]. The signals were digitized in the embedded module.  
The preliminary study for electrode positioning test was conducted on animals sedated with 1 mL/kg of Xylazine (Rompun from BayerTM), totaling 6 mL. For each position, signal collections were performed with durations ranging from 20 to 70 s, and from these collections, artifact-free segments were selected for analysis.  
This study was conducted using noninvasive electrodes consisting of 1.0 cm gold discs. Electrode fixation was attempted with either strong adhesive tapes or cyanoacrylate, also known as super glue (Super bonder--Loctite). First, the area at the forehead of the cows where the electrodes would be fixed was shaved. Then, the electrodes were filled with conductive gel for the EEG. Next, the animal module was placed in a small bag around the animal's neck. The module remained fixed for a month to facilitate the animal's adaptation to the equipment.  
The equipment comprised a single-channel electroencephalograph (bipolar measurement), so the sensor consisted of two electrodes to acquire the biopotential signal acquisition as well as a grounding electrode. The grounding electrode was positioned at the back of the animal's neck, whereas the other two electrodes were tested at three different positions (POS1, POS2, and POS3) of the animal's forehead. These positions were selected on the basis of the bovine head anatomy. Anatomical head sections were analyzed to investigate positions for electrode fixation. The images of heads that were used for this analysis were obtained at a local slaughterhouse, so they are not images of heads of the animals that were used in the experiments.  
After the establishment of acquisition conditions, a new experimental stage was initiated, and the signals were acquired from awake animals (free from sedation) in two situations: (1) from animals contained in a climatic chamber (cage containment) and (2) from animals in pasture (animals with freedom of movement).  
The main experiment involved twelve Holstein heifers, which were divided into two groups of six. In the first situation, the animals were contained in 1.0 \(\times\) 2.0 m individual cages arranged as a 2 \(\times\) 3 matrix inside a climatic chamber. In the second scenario, the animals were situated in enclosed compartments within an experimental paddock. These compartments measured 4.0 \(\times\) 3.0 m and were arranged side by side in a 1 \(\times\) 6 matrix. The cows had unrestricted access to food and water throughout the experiment.  
During the experiment, the temperature and relative air humidity were collected and used to determine the enthalpy of the place, as proposed by [PERSON] [59]. Enthalpy is considered an index of thermal comfort and reflects the environmental conditions related to the thermal stress experienced by the animals [60,61]. This stage of data acquisition lasted three full days.