Minas Gerais accounts for 27.6% of the national milk production, standing out as the largest producing state in the country. Although statistics show a constant evolution in the milk production chain in Brazil, in recent years dairy farming has faced new challenges and, in this scenario, with low profit margins, it is necessary to increase the efficiency of milk production systems, which still have many constraints. Among these, infecto-contagious diseases stand out, with mastitis being the main one in the economic aspect. This disease is characterized by an inflammatory response in the mammary gland usually caused by bacterial infections. This disease is characterized by an inflammatory response in the mammary gland usually caused by bacterial infections. As impacts to the activity can be cited the reduction of productivity and quality of dairy products, increased costs with labor and treatment of animals, milk dumping, as well as aspects related to food safety. A promising way to increase the efficiency of production systems is the selection of more productive and resistant animals. Therefore, studies with the purpose of better understanding the biological processes involved in the determination of resistance responses and production characteristics are fundamental in the development of technological solutions. Thus, the objective of this project is to evaluate the genes expressed in the alveolar tissue of extracorporeal mammary gland perfused and inoculated with Streptococcus agalactiae, one of the major causative agents of mastitis, using the extracorporeal gland model. In order to meet this objective, we will use the RNA-Seq methodology, which allows the overall evaluation of gene expression against a given condition. This characterization aims to identify the genes expressed in response to mastitis and to understand their regulation to better understand the pathophysiology of this disease, a strategy which can be used in more efficient treatments.