Corn silage and alfalfa hay occupy an important place among juicy and coarse fodder for cattle. Due to violation of the technology of procurement, storage or use of these fodders, a large part of them decays and becomes unsuitable for animals feeding. Getting such feed into the diet of ruminants can cause various negative consequences. Therefore, the problem of effective disposal of spoiled corn silage and alfalfa hay arises. One of the effective methods of spoiled feed of plant origin processing into organic fertilizer is composting using microbiological preparations - biodestructors. Composting accelerates mineralization and increases the assimilation of trace elements by plants. However, the problem of the influence of different doses of the BTU-CENTR biodestructor on the content of microelements in fermented corn silage and alfalfa hay has not been studied. For the study, samples of spoiled fodder had been selected, which were fermented without the introduction of a biodestructor (control) and with the introduction of a biodestructor in doses of 5.0, 10.0 and 20.0 cm3/t. The content of Ferrum, Zinc, Manganese, Copper and Cobalt was determined in hay and silage after composting. During composting of spoiled alfalfa hay, the Ferrum content in it increases relatively to feed before fermentation. In the control version, the increase in metal content was at the level of 40.0%. Fermentation of fodder with the participation of a biodestructor (use dose of 10.0 cm3/t) led to an increase in the content of Ferum in the composted biomass by 35.7% compared to the control group. During composting with the addition of a biodestructor in the amount of 20.0 cm3/t, the Ferrum content increases by 2.1 times relatively to the metal content in alfalfa hay before fermentation. During the composting of hay with the addition of a biodestructor, the mineralization process accelerated and the content of Zinc per unit of the fermented mass increased. The highest metal content was found in the experimental group where the microbiological preparation was used at a dose of 20.0 cm3/t. The difference with the control indicator was 49.6%. Fermentation of alfalfa hay without a biodestructor led to the fact that the content of Manganese was the lowest in relation to the research groups. The biggest difference was with fermented biomass biodestructor at a dose of 20.0 cm3/t and constituted 23.3%. The content of Copper in alfalfa hay after fermentation with a biodestructor increases significantly. It has been proven that the more biodestructor was used during composting of alfalfa hay, the higher was the metal content in the fermented mass. At the highest dose of the biodestructor, the content of metal-biotics in the fermented hay increased by a statistically significant value. The difference with the control group constituted 50.3%. The higher dose of the BTU CENTR biodestructor was added to the starting material, the higher was the Cobalt content in the composted hay. When a biodestructor was applied to alfalfa hay at a dose of 20.0 cm3/t, the metal-biotic content after composting was 26.7% higher than in the control group. A similar regularity was revealed regarding the change in the content of biotic metals in corn silage after its composting with a biodestructor. Fermentation of silage without the addition of a biodestructor was accompanied by an increase in the content of Ferrum, Zinc, Manganese, Copper and Cobalt in the composted biomass relatively to the feed before fermentation. The more the biodestructor was added to the corn silage, the more fermentation contributed to the increase in mineralization, and accordingly, the content of biotic metals in it. With the use of the largest dose of biodestructor, the content of Ferrum, Zinc, Manganese, Copper and Cobalt in fermented feed increases by 37.2, respectively; 41.3; 46.4; 21.6 and 30.0% relatively to the control group.