The organism of young cattle in postnatal ontogenesis can be considered as a system capable of effectively transforming feed nutrients into food protein and fat. The intensity of synthesis and accumulation of protein and fat in carcasses depends on the technological solutions used at all stages of beef production such as rearing and fattening. The purpose of the research was to study the character and intensity of protein and fat deposition in steers of Simmental breed, as well as the ability of their body to transform protein and metabolic energy of feed into the main nutrients of the beef of carcasses under conditions of various methods of housing. Using the method of pairs of analogues taking into account the origin, age and birth weight, 3 groups of steers with 15 heads in each were formed. The housing of steers of the 1st control group was in group-housed till 7 months, and then by keep tied method. Calves of the 2nd and 3rd experimental groups from birth to the age of 7 months were reared using the technology of beef cattle breeding on suckling method. After weaning from the cows, the steers of the 2nd experimental group were transferred to keep tied method, and the herdmates of the 3rd experimental group were transferred to free-stall housing. The slaughter of steers was carried out at birth, at the age of 6, 12, 15 and 18 months, determining the morphological composition of carcasses and the chemical composition of the average sample of meat, on the basis of which the conversion of protein and feed energy into food protein and fat of carcasses was calculated. It was found that weaning stress and free-stall housing negatively aff ected the ability of steers to transform protein and feed energy into nutrients of meat products, which resulted in a decrease in the conversion coeffi cients of protein, fat and energy. The value of the protein conversion coeffi cient at the end of the experimental period was in the 1st, 2nd and 3rd groups 6,7; 6,6; 6,1 %, respectively. The conversion coeffi cients of the metabolic energy of feed into fat and the energy of the edible part of carcasses in young animals of the 3rd experimental group aged 12, 15 and 18 months were, respectively, 1,4; 1,7 and 1,5 abs.% lower than in animals of the 1st control group.