Authors: А. I. DENKIN, candidate of biological sciences, senior researcher, Institute of Animal Physiology, Biochemistry and Nutrition – Branch of Federal Science Center for Animal
Husbandry named after L. K. Ernst (Institute of Animal Physiology, Biochemistry and Nutrition, 249013, Borovsk, Kaluga district; phone: +7 484 384-30-26; e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.),
V. О. LEMIASHEVSKIY, candidate of agricultural sciences, associate professor, International Environmental Institute named after A. D. Sakharov of Belarusian State University (23 Dolgobrodskaya Str., 220070, Minsk, Republic of Belarus; phone: +375 29 938-17-70, e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.)
Keywords: bulls, diet, metabolizable protein, substrates, energy balance, growth.
Abstract. In vivarium conditions of the institute animal on bull-calves of Kholmogor breed by the method of periods according to the Latin square scheme, the consumption, digestibility and assimilation of nutrients at different levels of metabolizable protein in the diet are studied by introducing feed additives with reduced protein disintegration (soybean meal). Experimental bull-calves, with an initial weight of 335 kg (10 months old), are grown according to the adopted technology using dairy products: whole milk and milk replacer, a mixture of rubbed concentrates, with early training for the consumption of coarse feed. The animals in the experimental groups received 4 different levels of metabolizable protein with a diet. The ratio of the metabolizable protein to the metabolizable energy of the diet was in the 1st group 7.8; in the second – 8.1; in the 3rd – 8.2 and in the 4th – 8.5 g/MJ. On the basis of the balance of energy and substrates, the ratio of the expenditures of the metabolizable energy of the ration for heat production and deposition in the weight gain of bulls during the fattening period is determined. The contribution of amino acids to the increase in production at different levels of metabolizable protein in the rations was: in the 1st – 48 %, in the 2nd and 3rd groups – 49 % and in the 4th group – 46 %. Increasing the level of metabolizable protein in the diet from 7.8 to 8.2 g per 1 MJ of metabolizable energy contributes to a more efficient use of metabolizable energy and amino acids for the increase in live weight. When the ratio of metabolizable protein to metabolizable energy is 8.5, the contribution of metabolizable energy and amino acids to the increase in production decreases, therefore, the normal level of protein nutrition for a given age, body weight and level of weight gain should be considered 8.2 g of metabolizable protein per 1 MJ of metabolizable energy.
