Abstract: This study was carried out to determine the effects of different additives on the nutrient composition, in vitro gas production and its parameters and the quality of alfalfa silage. Formic acid salts (F silofarm formiat dry; SD and F silofarm liquid; SL), biological inoculant (Sil All; SA) and molasses (M) were added to the raw material individually. Gas Production (GP) and its parameters were studied by using in in vitro GP technique with ruminally fistulated Sakiz x Karayaka rams vitro Krganic Matter Digestibility (IVOMD) and Total Energy (TE), Digestible Energy (DE), Metabolisable Energy (ME), Net Energy lactation (NEL), Net Energy fat (NEF), Net Energy maintanance (NEM) were studied by using in pepsin-cellulase method. SL increased Dry Matter (DM) content of alfalfa silage compared the other group silages (p<0.05) but decreased Crude Fiber (CF) (p<0.01). Molasses numerically increased the CP but the difference is no statistically significant. Molasses increased he Ether Extracts (EE) compared with Control Silage (CS) (p<0.05). SA addition into silage increased the ash of alfalfa compared wit CS (p<0.05). GP numerically is reduced by silages with additives. At 96 h incubation the total GP for SDS was significantly (p<0.05) higher than CS. the gas production from the insoluble fraction “b” value of silages was lower for MS compared with CS and SAS (p<0.05). MS and SAS improved the pH, lactic acidcontent and Flieg score of alfalfa silage but MS included butyric acid that it is undesirable in silages. The NH3-N concentration of the silages were the highest for MS and CS. The different additives addition into alfalfa silage decreased the ME, NEL and OMD values determined by using gas production technique. The energy values of alfalfa silages determined by using pepsin-cellulase method increased when they were ensiled with M and SL additives. Total energy values of silages determined by using pepsin-cellulase method different each other when they were ensiled with different additives.