The object is the studying of influence of some sources of nitrogen, energy, mineral elements and acceptors of hydrogen on the intensity of growth and metabolic activity of steers rumen microorganisms mixed population in conditions in vitro. The purpose is to find out the influence of various sources of nitrogen and energy, some mineral elements and their combinations, and also acceptors of hydrogen on growth and metabolic activity of rumen microorganisms in steers of different age in conditions in vitro. The methods of research and equipment are biochemical, microbiological, photoelectrocolorimeter, spectrophotometer, Markgam apparatus, аtomic-absorbtion spectrophotometer, pH meter, microscope. Innovation - the new data about the influence of various nitrogenous and energy compounds of forages and their combinations on the growth of rumen microorganisms population in steers from 1 till 6 months of age in conditions in vitro, their cellulolytic and amylolytic activity, the production of ammonia and low-molecular fatty acids were obtained. The influence of various mineral elements and their combinations on growth and metabolic activity of microorganisms of rumen of steers of 6 months of age in dependence on their concentration in incubation medium was investigated. The optimal quantities of different trace elements for microorganisms in rumen of steers were established. Three strains of phytateutilizing bacteria from the contents of rumen of steers were selected and their properties were investigated. The decrease of microorganisms growth intensity and processes of fermentation in rumen of steers with experimental atonia were revealed, and the stimulatory influence on these changes of sodium sulfate, zinc chloride and saccharose was established. The results - it was studied the dynamics of age changes of metabolism in rumen of steers from 1 till 6 months. It was investigated the influence on intensity of growth and enzyme activity of different concentrations of nitrogenous, energy and mineral compounds on the mixed population of rumen microorganisms of 1-, 2-, 3-, 4- and 6-months steers in conditions in vitro. It was established the optimal amounts of urea and glucose, and some mineral elements also, which provided the maximal growth of rumen microorganisms population. For the normalization of growth of symbiotic microflora and processes of digestion in steers with rumen atonia it was recommended to introduce per os a mixture of sodium sulfate, zinc chloride and saccharose. The inculcation - the results obtained will be used at the normalization of nitrogenous, energy and mineral feeding of calves. The sphere - biochemistry, physiology, therapy, microbiology, feeding
