The general objective of this project was to identify microbial strains that produce enzymes capable of degrading fibers or hydrolyzing secondary anti-nutritional compounds, aiming to identify microbial isolates (rumen bacteria or fungi) with fibrolytic capacity or tolerant to anti-nutritional factors, as well as to expeditiously isolate and characterize fibrolytic enzymes. It was also the objective of this project that the use of laboratory procedures would serve to train undergraduate and graduate students from partner universities of the Embrapa dairy Cattle’s rumen microbiology laboratory. It is intended that, in the long term, microbial strains isolated for tolerance to secondary compounds or with high fibrolytic capacity can be produced on a large scale, that is, industrially, and supplied to ruminants, in order to increase the efficiency of feed use for the production of milk and beef.