A, Malinovskaya ul., St Petersburg—Pushkin, 196602 Russia, е-mail deniz@biotrof.ru Supported by the Russian Science Foundation, the project ¹ 14-16-00114 Received September 8, 2014 Abstract The presence of mycotoxins in the feeds is a big problem in the world. <...> Result of improper silaging is the occurrence of mycotoxins, the metabolic products of molds. <...> Today there is too little information on the accumulation of mycotoxins in silage during ensiling, and there is no answer to the question how to resolve this problem. <...> This article includes results of mycotoxins' analysis (aflatoxins, ochratoxin A, T-2 toxin, zearalenone, deoxynivalenol) in the original forage plant material of cocksfoot Dactylis glomerata L. and in the silage at various stages of experimental ensilaging. <...> Also the influence of biological preparations Biotrof and Biotrof-111 (Biotrof+ Ltd, Russia) and chemical preparations AIV 3 Plus and AIV 2000 Plus (KEMIRA OYJ, Finland) for the preservation of silage on reducing the amount of toxic fungal metabolites was investigated. <...> Analysis of the amount of mycotoxins in the samples was performed by the enzyme immunoassay method using ELISA test kit AgraQuantTM (Romer Labs, Inc., Austria). <...> Analysis of the accumulation of mycotoxins in feed plant material and silage showed that mycotoxins already occurred in forage plants as a result of fungal attacks during the growing season and later in the silages if conditions were suitable for mold growth. <...> At the end of silage storage the amount of aflatoxins in the variants with Biotrof and Biotrof-111 was lower by 17.7 and 9.1 %, respectively, compared to the control, with a decrease in the value of ochratoxin A by 21.4 and 34.9 %, T-2 toxin by 20.1 and 32.8 %, zearalenone by 17.7 and 10.4 %, and deoxynivalenol by 0.8 and 55.8 %, respectively. <...> So far as in Russia no maximum permissible concentrations are specified for mycotoxins in silage, the values for feed grain of oats, wheat and barley taxonomically close to perennial cocksfoot grass were used for comparison (corn, one more cereal crop, is not a traditional forage plant in the North West region of Russia). <...> The greatest deterrent effect on accumulation of mycotoxins had the preparation based on Bacillus subtilis. <...> However, the silage' total toxicity in presence of the chemical preparation was quite high relatively the maximum permissible concentrations used in this study as the reference values. <...> As it is <...>