Mycotoxicological monitoring of forages shows that the problem of mycotoxicosis has been relevant for several decades. Minimal doses of mycotoxins in feed lead to a decrease in milk productivity, increased sensitivity to infectious and non-infectious diseases. When several mycotoxins enter the body simultaneously, a synergistic effect develops, causing a significant increase in toxicity. Feed contaminated with several types of fungi and their toxins is dangerous for dairy cattle. It was found that the feed mixture contained the types of associations of Aspergillus spp. fungi + Fusarium; Aspergillus spp. + Penicillium spp. + Mucor spp; Fusarium + Penicillium; Mucor spp. + Fusarium + Ustilaginales. Pathogenetic features of metabolic and morphological changes in highly productive cows with polymycotoxicosis were studied. Feeding food contaminated with various metabolites of mold fungi leads to the development of signs of chronic toxemia in animals. Clinical manifestations are the development of diarrhea and dehydration, with a decrease in milk productivity. Metabolic disorders feature the development of an inflammatory process, metabolic acidosis, hyperfermentonemia, with an increase in the amount of creatinine and urea in the blood serum. Metabolic signs indicate the development of hepatorenal syndrome due to structural disorders of the liver and kidneys. Histological signs of polymicotoxicosis are intracapillary and hemorrhagic glomerulonephritis, hepatocyte micronecrosis, and proliferation of connective tissue stroma cells, which leads to the development of atrophic cirrhosis in the interstitial and circular phases.