Data are presented on the effect of hay from mixtures of sweet sorghum plants Galiya 85% with Siberian fodder beans 15%, preserved with the probiotic preparation Microbiovit Enisey at a dilution of 1: 100, according to consistent indicators of fattening bulls. Research based on the branch of the Federal State Budgetary Institution “Omsk Agrarian Scientific Center” RPF (Research and Production Farm) “Omsk” on 6-9-month-old fattening bulls in the amount of 18 heads, divided into three groups of 6 animals: a control and two experimental ones, in the diet of which silage with a preservative, was prepared. And without it. The diet is designed by age and live weight. Feed intake daily. In the comparative period, appetite and feed intake were the same in all groups – 80%. During the transition period, in the 1st and 2nd experimental groups, appetite and palatability remained at the same level, and in the control group, palatability increased by 10%. During the main period in the control group, feed intake remained at the same level - 90%, and in the 1st and 2nd experimental groups, it increased to 100%. As a result of complex studies of feces and biochemistry of blood serum, the following conclusions were made on the leading indicators: indicators of enzymatic (AST, ALT), mineral (Ca, P, Mg), and carbohydrate (glucose) metabolism, substances within normal limits for all groups, alkaline level. Phosphatase was higher than usual, which indicated increased growth of animals. The indicators of protein metabolism, total protein, and creatinine at the end of the main experiment were higher than in the equalization and transition periods; the urea content was at the average normal limits in all main groups. The organoleptic scatological examination and the biochemistry of feces show that the digestive processes of all the animals provided are not impaired. It was noted that bull calves that ate strength preserved by Microbiovit Yenisei had no indigestible fiber due to better digestion.