Mold growth in feed leads to adverse effects associated with the reduction of its nutritional value, production of mycotoxins (toxic secondary metabolites), and allergenic spores, which are risk factors for animal and human health. Aflatoxins, synthesized especially by strains of the genus Aspergillus are the best known mycotoxins. The presence of aflatoxins in feed is connected with the growth of mold in the time of harvest and during storage of agricultural products, which are used in animal feed. The possibility of biotransformation of aflatoxin B1 in dairy cattle and the accumulation of products of the reaction - the aflatoxin M1 in milk is another threat. For many years there were conducted researches into ways of reducing mycotoxin contamination of feed, either by inhibiting the growth of fungi and thus the production of mycotoxins by them and through detoxification of material contaminated by chemical, physical and microbiological methods. The latter method seems to be the most suitable for practical use in decontamination of contaminated plant material. Researches on the biological inactivation of aflatoxins and inhibition of growth of toxigenic fungi are still held in a narrow range and comprise mainly fermentation processes. Among many microorganisms having the ability to degrade mycotoxins the lactic acid bacteria are of particular interest. Bacterial preparations for silage feed, which include the bacteria strains with the special ability to reduce the level of aflatoxins are examples of their practical application. In this paper there was proved a positive effect of bacterial starter culture on decreasing the content of aflatoxins in meadow grass silages, even above 90% with respect to its initial content.