Alfalfa silage is a useful source of protein for feeding ruminants. Therefore, managing alfalfa silage in livestock production systems is an important issue in order to maintain the silage quality and achieve maximum profitable production of milk and meat. The aim of this investigation was to estimate the effects of bacterial inoculant Silko, containing Lactobacillus plantarum (strains: LP1, LP2, LP3 and LP4) on chemical composition, energetic characteristics and fermentation alfalfa silage under field conditions in the commercial dairy farm, during the 2016. The first-cut alfalfa in the second year has been conserved in silage form. The silage mass was subdivided into two equal parts (control (silage without inoculant) and silages treated with bacterial inoculant Silko) and ensiled in trench silo. After 60 days of ensiling, the silages were analysed. Dry matter, ash, crude protein, lactic acid, acetic acid, total digestible nutrients value and relative feed value were significantly higher in silage treated with bacterial inoculant Silko compared to control. Contrary, alfalfa silage treated with a bacterial inoculant Silko had lower values of cellulose, acid detergent fibre, neutral detergent fibre, nonnitro extractive matter, pH, butyric acid, soluble nitrogen/total nitrogen and NH3- N/total nitrogen than untreated silage. Results showed that bacterial inoculant Silko increases silage quality compared to control so that research should be directed toward the use of such prepared silage in ruminant diets and its impact on milk and meat production on farms.