## 1 Introduction  
Current livestock production has assumed an intensive nature, being characterized by compact farms, high input use and production in collective facilities, with the presence of thermal conditioning systems and some level of automation. These strategies, used in intensive animal systems, make it possible to increase the number of animals housed in terms of productive indexes and therefore ensure the safe supply of animal products [1, 2]. Choosing the facility type is a crucial step. It must be chosen considering aspects related to the local reality (climate conditions, techniques, materials and construction costs, labor for operation and maintenance, return on investment, etc.) and the needs of the animals to be housed (thermal comfort, health, and performance) [3, 4, 5, 6]. For dairy cattle, in particular, the compost-bedded pack barn (CBP) system, considered an alternative to traditionally used systems (tie-stall (TS) and free-stall with cubicles (FS)), has been gaining prominence and use worldwide in the last decades [7, 8, 9, 5, 6, 10]. In CBP, the cows are housed in collective facilities with bedding made of soft and comfortable organic materials, which, together with the excrements deposited by the animals and under certain conditions, decompose over time--Figure 1[11, 12]. Bedding composite in CBP systems is a biological process influenced mainly by factors such as temperature, moisture, hydrogen potential (pH), and concentrations of carbon and nitrogen in the bedding, as well as the oxygen availability [13; 14; 15]. Ideally, these parameters should be controlled within adequate ranges so that adequate decomposition levels of organic matter are ensured and, consequently, pathogenic microorganisms are eliminated and compost with good agronomic quality is generated [13; 16; 17]. The importance and general recommendations for these bedding parameters in CBP systems are: * Bedding temperature: A parameter directly related to the decomposing microorganisms' activity, as the more intense this activity is, the greater the heat production. In the CBP's aerobically active layer (0.15 to 0.30 m) it is desirable that it be maintained between 43.0 and 65.0 \({}^{\circ}\)C [11; 13; 14; 16]; * Bedding moisture: A variable associated with the metabolic activity of decomposing microorganisms, including oxygen availability in the bedding and the animals' manure. It is recommended that its levels be kept in the range of 40.0 to 60.0%, ensuring the maintenance of aerobic conditions and the survival of decomposing microorganisms [7; 11; 14; 18; 19]; * Bedding hydrogen potential (pH): A parameter associated with the enzymatic activity and development of decomposing microorganisms. It varies according to the composting process stage and the material used, but it is recommended that it be kept in a range of between 5.5 and 8.5 [13; 14; 20; 21; 22]; * Bedding carbon (C) and nitrogen (N) available: Especially important for decomposition activity, it is normally evaluated through the C:N ratio, since C and N are used for energy supply and protein synthesis, respectively. It is recommended that higher C:N ratios be provided at the beginning of the composting process (25:1 to 35:1), as most of the assimilated carbon (\(\approx\)66%) is eliminated in the form of carbon dioxide (CO\({}_{2}\)) and only part of it is immobilized and incorporated into the cellular protoplasm. With the degradation of organic matter during the composting process, there is a reduction in the C:N ratio, and it is important that C source materials are provided (wood sawdust, wood shavings, etc.) so that the composting process is not diminished [7; 13; 16; 23]; * Bedding oxygen available (O\({}_{2}\)): A crucial factor, as it is related to the respiration of aerobic decomposing microorganisms. The required O\({}_{2}\) concentration is a function  
Figure 1: Schematic representation of the bedding composting process in a compost-bedded pack barn system (emphasis on the bedding turning). C:N—carbon:nitrogen ratio; M\({}_{\text{B-Dep.