## 3 Results and Discussion
### Physicochemical Characterization
In order to improve the oxygenation rates and direct bedding drying, ventilation systems buried under the bedding can be used, such as the one described by [PERSON] and [PERSON] [32], which made it possible to maintain good aeration levels and, consequently, intense composting activity (\(>\)t\({}_{\rm B\cdot Dep}\)) and control over M\({}_{\rm B}\)--Table 3.  
Bedding hydrogen ion potential (pH\({}_{\rm B}\)) was another widely used parameter for evaluating bedding quality in CBP systems, being present in 10 of the 12 listed works--Table 3. In these studies, pH\({}_{\rm B}\) analyses were performed using bedding samples collected at the surface (pH\({}_{\rm B\cdot Su}\); \(n=4\)) and/or at depth (pH\({}_{\rm B\cdot Dep}\); \(n=9\)), and the occurrence of pH\({}_{\rm B}\) values ranging from acidic (5.5, [PERSON] and [PERSON] [32]) to basic (11.0, [PERSON] et al. [28]) was denoted. The pH range considered ideal for most decomposing microorganisms is between 5.5 and 8.0 [20; 50], which can be extended to 8.5, since most enzymes are active up to this limit [21]. The pH values in CBP systems are variable according to the stage of the semi-composting process: initially, it is predominantly acidic (5.0-6.0) due to the release of short-chain organic acids; throughout the process, these acids are consumed and the pH is raised to neutral or slightly alkaline (7.0-8.0); in the final stage, the organic acids have already been completely consumed, and the pH of the material is normally alkaline (8.0-9.0) [13; 22; 29; 51; 52]. In the listed studies, there was a higher prevalence of pH\({}_{\rm B}\) values \(>7.0\), and only in those conducted by [PERSON] et al. [30], [PERSON] and [PERSON] [32], and [PERSON] et al. [33] were values below the limit were found--Table 3. The studies carried out by [PERSON] et al. [30] and [PERSON] et al. [33] described bedding characteristics in CBP systems located in Minnesota (USA) and Rio Grande do Sul (BR), respectively, and the occurrence of minimum values lower than 7.0 may be related to the short use time and/or with recent bedding replacement with dry materials in some of these systems. In the study conducted by [PERSON] and [PERSON] [32], in which the composting process was comprehensively evaluated over time, the prevalence of pH values \(<7.0\) occurred only in the first 30 days of composting (from November to December 2013), resulting from the release of organic acids, common in the initial stage [51]. In most studies in which pH\({}_{\rm B}\) was evaluated, there was a higher prevalence of values \(>8.0\) ([PERSON] et al. [19], [PERSON] et al. [5], [PERSON] et al. [29], [PERSON] et al. [4], and [PERSON] et al. [27]--Table 3), which is an indication that the semi-composting process in these systems was already in the final stage [51; 52]. Even in studies in which minimum pH values lower than 8.0 were obtained, such values were not very representative, as reported in the study conducted by [PERSON] et al. [28], in which the pH of the bedding material was greater than 8.0 in 99.0% of the bedding area. According to the latter authors, pH values \(<8.0\) were determined only for samples from places where there was a high frequency of bedding replacement to reduce moisture, such as in the vicinity of evaporative cooling systems and/or drinking fountains. Notably, the occurrence of very high pH values (\(>\)9.0), as reported in some studies, can increase nitrogen losses ([PERSON] et al. [30], [PERSON] et al. [33], [PERSON] et al. [28], [PERSON] et al. [4], [PERSON] et al. [34], and [PERSON] et al. [27]). The assessment of bedding quality in CBP systems was also performed using its chemistry or nutritional composition--Table 3. In terms of the composting process, its importance refers mainly to the succession of decomposing microorganisms, which need certain levels of C and N to supply energy and to synthesize proteins, respectively [7; 23].