The Compost Barn system has the purpose of reducing costs in the implementation and maintenance of animal facilities, improving herd production and sanitary indices, and enabling the correct use of dairy farming organic waste (feces and urine). The system consists of a large covered space for the cows to rest. The floor is covered with sawdust, wood cutting scraps and composted manure. The main objective of Compost Barn is to ensure comfort to the animals and a dry place for them to stay during the year and the composting of bed material. The method harmonizes livestock production and environment, since it is based on the action of microorganisms that use the organic matter as a substrate. The Compost Barn system can offer an alternative for increased productivity to small and medium scale farmers, besides enabling greater comfort and hygiene for the herd, aiding in the reduction of leg and hull problems, diminishing the somatic cell count (SCC), increasing rut detection and milk production, and reducing the incidence of odor and flies. Currently, some dairy farms in Brazil have implemented the system for heifers and lactating cows. In this project the system features are being characterized in dairy farms located in the Sul de Minas region regarding sanitary and milk quality parameters (SCC, TBC – total bacterial count, evolution of the microbial flora of the udder, incidence of environmental mastitis and new cases of mastitis), reproduction (service period and calving interval), locomotion (hull infections), and animal behavior and welfare. Also, evaluations are carried out on microbiota (bacteria and protozoa), physicochemical characteristics of the compost over time and on the costs for the implementation and maintenance of the system. The project has the partnership of UFJF (Federal University of Juiz de Fora).