Silage is a common widespread practice to preserve forages in Brazil. One of the main problems encountered is the high value of rations and raw materials, so use mainly corn, sorghum and agro-industrial sub products. Being reviewed mycobiota present in the ensiled material and mycotoxins levels are an indicator of quality, because the poor storage conditions can lead contamination and toxins production. The research evaluated the quality of silages preserved with biological inoculants on mycobiota, mycotoxins levels and nutritional assessment parameters. Two dosages of commercial inoculant product, with 10 replications was used on corn silage and evaluated at 0, 30, 60 and 90 d. Fungal counts were done by surface-spread method and toxigenic ability of isolates strains was evaluated with in vitro conditions. Aflatoxins (AFs), ochratoxin A (OTA), fumonisin B1 (FB1) and deoxinivalenol (DON) natural contamination was determined with immunoaffinity columns extracts in HPLC. Total fungal counts were generally high (range 1.0 × 10⁶ to 1.0 × 10² cfu g⁻¹). Aspergillus flavus, Penicillium citrinum, and Fusarium verticillioides were the prevalent toxigenic strains isolated. Mycotoxins levels differed (P < 0.001) from pre and post-fermentation samples, probably due to mold growth. Dry matter, carbohydrates, lipids, protein, volatile fatty acids, and fiber content not differed (P < 0.001) from pre and post-fermentation samples and were not different from literature. The inoculants does not helped in reducing the count of fungal propagules but decreased the biodiversity of the toxigenic strains presents in the treated silos. So, the use of microbial inoculant on silage production should be recommended to reduce some toxigenic strains contamination. However, each product must be evaluated and the applying process must be carefully conducted. The mycotoxin binding and nutritional quality increase related on literature was not observed on the present study.