The problem of low-quality protein in the diet of animals leads to excessive formation of a by-product (ammonia) in the rumen, which is not involved in the synthesis of microbial protein. The aim of the study is to develop a method for the prevention of protein deficiency in dairy bull calves. Bull calves of Kholmogorsk breed were grown in the vivarium of Institute under the controlled feeding and keeping conditions from 40 days of age to 14 months. Milk replacer feeding was carried out up to

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... days of age with free access to mixed feed and hay.In order to study the effect of concentrated feeds on metabolic processes and digestibility of nutrients, rumenal digestion factors were studied. It was found that physiological and biochemical parameters fit into reference values. The use of concentrated feed together with strict proportional administration of roughage during intensive growing and fattening of bull calves of dairy breeds makes it possible to reach an average daily increase of up to 1420 g by the age of 14 months and effectively pay for the feed with the productsupon the normal course of enzymatic processes in the rumen and throughout the body.