Supplementation with additives containing live cells of microorganisms and / or their metabolites, known as probiotics and prebiotics, is increased in response to the demand for the use of "natural" growth promoting substances that improve the efficiency of production in cattle. Supplementation with beneficial microorganisms is expected to prevent the establishment of undesirable (pathogenic) microorganisms or to reestablish the normal microflora of the digestive tract. Several cases of increased animal performance are documented when cattle were supplemented with live microbial additives. The mechanisms proposed to increase this animal performance are related to the production of antimicrobial compounds such as acids and bacteriocins. In many countries this is already a routine practice and is used in livestock production mainly in the creation of calves affected by post-weaning diarrhea and in cows with high milk production that frequently contract acidosis due to excessive intake of soluble carbohydrates. In Brazil, the interest for the use of products of this nature is increasing; however, the cultures used are imported, which increases the cost of production. It is in the interests of producers to use more specific and effective crops of a national origin, which will result in lower financial charges and more profitable activity. The objective of this project is to build a collection of potentially probiotic microorganisms isolated from ruminal fluid and bovine feces to be provided as an additive to improve animal health and performance. These microorganisms are identified and preserved as part of collection in permanent construction meant to establish a genetic resource base for the research and development of technologies for the farmer. In selecting bacterial strains for the preparation of the probiotic, the microorganisms should survive the barriers found along the gastrointestinal tract, so that they can be implanted and multiplied. After passing through a series of evaluations such as: growth capacity, ruminal fluid multiplication, resistance to hydrochloric acid, bile salts and high temperatures and salinization, among others criteria, Microbial strains belonging to the genus Lactobacillus, Bifidobacterium, Enterococcus and yeasts are considered potentially probiotic. Microorganisms exhibiting different morphological characteristics and behaving as good survivors under the conditions of the tests performed are identified by biochemical tests and sequencing of a ribosomal rDNA region, 16S for bacteria and the ITS1-5.8S-ITS2 region of the rRNA gene for yeast or sequencing the large subunit {D1 / D2 region of the large subunit of the 18S ribosomal RNA gene. The selected strains will be tested in vitro for the ability to inhibit the growth of pathogenic microorganisms and to mitigate enteric gases, respectively. To do this, solid-media inhibition tests using Gram positive and Gram negative bacteria will be performed as indicators of probiotic potential and the measurement of CO 2 and CH 4 gases and volatile fatty acids. Thus, it is expected to isolate and characterize microorganisms with potential use as probiotic and technological, considering the great potential of these additives and the importance of having national products for application in dairy cattle.