Improvement of the standards of energy and protein diets of young stock cattle of 1-6 month old and determination of its influence on animal productivity was realized in the conditions of the Republic of Belarus. The studied made it possible to determine that at the age of 1 month the calf diet should contain 1,02 kg of dry matter and 21,2 MJ of metabolic energy; at the age of 2 months - 1,26 kg and 23,5 MJ; at the age of 3 months - 2,2 kg and 25,6 MJ; at the age of 4 months - 2,9 kg and 31 MJ; at the age of 5 months - 3,28 kg and 34,2 MJ; at the age of 6 months - 3,76 kg and 37,6 MJ, respectively. Metabolic energy concentration per 1 kg of dry matter should not be lower than 20,7 MJ at the first month, 19 MJ - at the second month, after the third month it should lower up to 10 MJ. In course of 6 months the presented diet scheme made it possible get 832 g of average weight gain in the conditions of forage expenses of 3,52 forage units per 1 kg

The level of yielding and biological capacity of grass mixtures of feeding crops (common ryegrass (Lolium perenne); spring vetch (Vicia); Austrian winter pea (Pisum arvense); blue lupine (Lupinus angustifolius); common barley (Hordeum vulgare)) in the conditions of the Northern part of the Republic of Belarus and their quality evaluation were studied. The optimum temperature of seed germination at the seeding depth and the sufficient amount of moisture in soil provided high germination rate. Nitric fertilizer application and crop sowing in the conditions of various coenosis did not affect seed germination. The quantity of shoots predetermined the optimum plant stand density and made it possible to generate high green mass productivity. Formation of a high green mass yield in single-crops sowings of annual ryegrass was obtained against the background of minimum 180 kg of primary nutrients of nitric fertilizers per 1 ha, taking into consideration that the amount of crop tops increases in 3 times in comparison with crops without nitric fertilizers. Inclusion bean component into the grass mixture (even without nitrogen application) made it possible to generate the level of top biomass by three hay crops from 40,2 up to 55,4 t/ha. However, application of mineral nitrogen for cultivation of leguminous and cereal crop mixtures with overgrassing of annual ryegrass made it possible to increase the green mass productivity. Inclusion of a bean component into a grass mixture rendered influence on the amount of digestible protein. The highest protein yield was provided by high yielding crops with content of spring vetch on the background of mineral nitrogen (0,9 t/ha). In coenosis with pea and lupine mixtures provided protein content of 0,8 t/ha

The comparative analysis of application of cereal ensilage produced with addition of microbial and enzymatic preserving agents Axphast Gold and Biotrof on fodder digestibility, hematological indexes and cicatrical digestion of cattle rearers was realized in the conditions of the Republic of Belarus. Cattle feeding with the analysed silage rendered positive effect on digestibility of the forage dry matter, which was on 2% higher the control index, organic matter - on 2,4%, nitrogen-free extractive substances - on 2,84%, fat - on 0,58%, protein - on 2,3%, cellulose - on 2,1%. Use in feeding of ensilaged forages from the cereal perennial grasses preserved by the microbial- enzymatic preparation produced by company Biota rendered the positive influence on use of nitrogen, calcium and phosphorus. There was also noted the increasing of the content of volatile fatty acids in paunch of young cattle silage fed with Axphast Gold that testified of more effective utilization of forage

Balanced complete feeding proved to be one of the major conditions of animal productivity increase and improvement of their reproductive qualities. Full value of feeding could be obtained at the expense of forage quality improvement and perfection of structure of the rations providing the increasing of metabolic energy use by breeding bull-calves. Analysis of the efficiency of metabolic energy use by the replacement bull calves under conditions of various sugar and protein ratio was realized in the Republic of Belarus. Research results showed that enrichment of replacement bull calves (with 325-405 kg of live weight) rations with easy digestible carbohydrates (sugar and starch) in ratio of 32% from a dry matter ration, including 15% of stable starch made it possible to increase the transformation of metabolic energy into energy of body weight gain on 21,73 - 23,96 MJ or on 10,3%, that as a result correspondingly increased the daily average weight gains on 7,9% and reduced the expenses for forage energy for 7,1% counting on an energy unit. According to the ejaculate volume indices the bull calves of the second experimental group surpassed analogues of a control group on 14,8%, and according to sperm concentration indices - on 12%. The average quantity of the frozen doses of sperm has made 65%