Alfalfa silage has a high potential for improving ruminant nutrition. A problem that frequently occurs during its preparation is the process of proteolysis, which could partially be avoided with the use of certain techniques and materials. Red clover, often used in form of silage, expresses weaker proteolysis due to the possession of certain chemical compounds. This research was conducted to study the effects of ensiled alfalfa and red clover mixtures, mixed at different ratios (100:0, 90:10, 70:30, 50:50, 30:70, and 0:100), as well as the influence of additives – two doses of oak tannin extract (6 g kg-1 DM and 12 g kg-1 DM) and bacterial inoculant (Enterococcus faecium, Bacillus plantarum, and Bacillus brevis) on fermentation parameters and protein fractions of the silages. The treatments which contained any of the used percentages of red clover, as well as the ones which received the higher dose of oak tannin (12 g kg-1 DM), reduced the ammonia nitrogen content, which is one of the main indicators of proteolysis. On the other hand, considering non-protein nitrogen, as another of the indicators of proteolysis, there was no positive sign of the contribution of red clover to the reduction of proteolysis in alfalfa, and neither there was a significant impact of additives that were applied in this experiment.