The results of researches of products of slaughter of Simmental bream bulls for various selenium-containing additives in the diet are presented. Determination of the morphological composition of carcasses has shown the advantages of experimental groups of animals before the control of the high content of pulp in the carcass (6.1-8.2 kg) and a slightly higher ratio of meat (0.05-0.08). In the carcasses of experimental bulls, bone content decreased (18.7-18.9% versus 20.1% in control). It should be noted that the best results from meat productivity were obtained in the group of animals fed with the diethylvanic preparation Devivit in the diet. In samples of meat of bulls of experimental groups, it was unambiguous, although biometric and unreliable (P>0.05), it was less on 0,28-0,55% of water (76,41-76,14 against 76,69%), and more on the same amount of dry matter. The introduction of selenium supplements in the diet of bulls of the 1st and 2nd experimental groups resulted in an increase compared with the control of muscle protein content by 2.9 and 4.4 absolute percent (P>0.05), while the concentration of fat in this case, on the contrary, fell by 14 and 17.1% respectively (P>0.05). The level of tryptophan in the animal meat of experimental groups was higher than control at 2.29-4.4 mg%, and oxyproline, which reflects the worst grades of meat, on the contrary, was less on 1.31-4.25 mg%. As a result, the protein-quality index (the ratio of tryptophan to oxyproline) in experimental samples of meat was different from the control at 0.2-0.5. At tasting meat estimation on qualitative indices of broth on a 3-point system, no significant difference between groups was found. However, the tasting score of boiled meat of bulls of experimental groups, which was conducted on a 5-point system, averaged 4.35, and controls - 4.17 points, which is 4.1% less than the evaluation of samples of meat experimental animals. There is a probable increase in the activity of aminotransferases in liver tissues - 2.28 ± 0.04 (p<0.05), as well as soluble protein in muscle tissues - 58.39 ± 2.33 (p<0.05) and 114, 76 ± 5,13 liver (p <0,01) of experimental bulls. According to the results of studies of some trace elements in the tissues of the longest muscle of the back, liver and heart of the bulls, no significant differences were observed between the control and experimental animals. In the fattening young, the selenium content in the oblong muscle of the back fluctuated within 0,042 (control) -0,087 mg / kg, which is completely acceptable and safe. From this it can be concluded that beef can be one of the sources of replenishment of the lack of selenium in the human diet. When comparing experimental animals with serum selenium control after 3 months after the start of the experiment, they exceeded the control at 0.031-0.047 μg / ml or 39.2-75.9%. And after 6 months the excess was already 0,033-0,067 μg / ml, or 38,8-58,7%.