The new silage preparation (AFSil) is an autolysate of biomass of the non-pathogenic soil fungus Cephaliophora tropica D3, grown in an environment enriched with trace elements. The fungus selectively uses ammonia from the nutrient substrate, and thus also contributes to lowering the pH of the culture medium. The use of the product is recommended to reduce the risk of proteolysis in ensilage of alfalfa that is difficult to slightly difficult to ensile, especially with higher dry matter, higher nitrogen content and longer cuttings.