Abstract: The effect of epiphytic microorganisms and exogenous Lactic Acid Bacteria (LAB) on the formation of Non-Protein Nitrogen (NPN) components during the ensiling process was investigated. All silages were prepared in mini-silos of 100 mL polypropylene centrifuge tubes and kept in an incubator at 30°C and tubes of each treatment were opened after 1, 3, 7, 14 and 35 days of ensiling. Treatments included three variations: nothing added (control); epiphytic microorganisms killed (treated with Ultraviolet (UV) rays) and xogenous lactic acid bacteria (inoculants of lactic acid bacteria after treatment with UV rays) added.